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GCSE Revision Flashcards > GCSE Astronomy - Pearson Edexcel - COMPLETED > Flashcards

GCSE Astronomy - Pearson Edexcel - COMPLETED Flashcards

*NOT MY QUESTIONS, COPIED FROM ANOTHER DECK - CREDIT: ASHRAF AHMED GCSE ASTRONOMY 9-1 FLASHCARDS*

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1
Q

What is the Earth’s mean diameter?

A

13,000 km

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2
Q

What is the largest terrestrial planet?

A

Earth

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3
Q

What shape is the Earth?

A

Oblate Spheroid

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4
Q

How is the Earth an oblate spheroid?

A

The polar diameter is smaller than the equatorial diameter by 42 km

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5
Q

How much of the Earth is covered by water?

A

~70% (71%)

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6
Q

What are the Earth’s 4 major internal divisions?

A

Crust, Mantle, Outer Core, Inner Core

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7
Q

What is the thickness of the Earth’s crust?

A

The Earth’s crust ranges in thickness from 0-70 km thick

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8
Q

What is the continental crust made up of?

A

Low-density rocks such as granite

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9
Q

What is the thickness of the Oceanic crust?

A

Up to 10 km thick

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10
Q

What is the Oceanic crust made up of?

A

Denser rocks such as basalt

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11
Q

What does the crust float on?

A

The silicate mantle

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12
Q

How much of the Earth does the mantle make up?

A

~80% of the Earth’s volume

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13
Q

What is the state of the mantle?

A

Semi-molten/liquid

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14
Q

Why do the tectonic plates move?

A

As the upper mantle is semi-molten, the thermal convection currents rise and fall, driving the sideways motion of the tectonic plates

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15
Q

How hot is the outer core of the Earth?

A

~5000 K

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16
Q

What materials is the outer core made out of?

A

Liquid iron and nickel

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17
Q

How is the Earth’s magnetic field created?

A

Currents of charged particles that flow in the outer core are responsible for the Earth’s magnetic field

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18
Q

What is the state of the inner core?

A

Solid

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19
Q

What is the temperature of the inner core?

A

~5500 K

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20
Q

Why is the inner core solid?

A

The high pressure prevents the iron and nickel from melting

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21
Q

What is latitude measured in?

A

Degrees North or South of the equator

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22
Q

What is longitude measured in?

A

Degrees East or West of the Prime Meridian

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23
Q

Where is the Prime Meridian?

A

In 1884, the Meridian passing through the Observatory of Greenwich was globally adopted as the zero of longitude

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24
Q

How much is the Earth’s polar axis tilted by?

A

23.5 Degrees to the vertical

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25
Q

When does the Sun lie directly over the equator?

A

March 21st and September 23rd; these dates also correspond to the vernal and autumnal equinoxes

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26
Q

When does the Sun lie directly over the Tropics of Cancer? (23.5 Degrees North)

A

21st June; this is also the summer solstice

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27
Q

When does the Sun lie directly over the Tropics of Capricorn? (23.5 Degrees South)

A

21st December; this is also the winter solstice

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28
Q

What are the Arctic and Antarctic Circles?

A

The Arctic and Antarctic Circles represent the most Northern (66.5 Degrees North) and Southern (66.5 Degrees South) latitudes

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29
Q

Why is the atmosphere important?

A

The atmosphere:
1. Provides us with oxygen to breathe
2. Absorbs harmful UV and X-radiation
3. Regulates our planet’s temperature to mean 15 Degrees Celsius
4. Protects us from most meteoroid strikes

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30
Q

What are the drawbacks of the atmosphere?

A

The drawbacks of the atmosphere are:
1. The sky is blue restricting observations to night time
2. Light is scattered by oxygen and nitrogen molecules in our air; most scattering occurs at shortest (blue) wavelengths so the sky is blue
3. Air is in the atmosphere and is consistently in turbulent motion. Different densities of air rise and fall on a variety of scales causing light to react and change direction as it passes through the different layers making the stars ‘twinkle’

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31
Q

What difficulties may astronomers face when observing?

A

Some major problems are:
1. Skyglow (the rusty orange haze caused by lights near urban communities)
2. Local glare from things like streetlights ruin astronomer’s dark adaptation

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32
Q

What are the 2 most common elements in the Earth’s core?

A

Iron and nickel

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33
Q

What are the 2 most common elements in the Earth’s crust?

A

Silicon and oxygen

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33
Q

What evidence is there that proves the Earth is a sphere?

A

Evidence:
1. Satellites orbit the Earth
2. Ships disappear over the horizon
3. The Earth casts a curved shadow during an eclipse
4. Aircraft fly in arcs (not straight lines)
5. Images of the Earth from space

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34
Q

What is the polar axis of the Earth?

A

The line around which the Earth rotates?

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35
Q

How much is the Earth’s axis inclined to the ecliptic?

A

66.5 Degrees

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36
Q

Which direction does the Right Ascension move?

A

Eastwards

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37
Q

Name 7 features on the Near side of the Moon:

A
  1. Ocean of Storms
  2. Copernicus Crater
  3. Kepler Crater
  4. Sea of Crises
  5. Apennine Mountains
  6. Sea of Tranquillity
  7. Tycho Crater
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38
Q

How are Lunar Maria formed?

A

Lunar Maria were formed by ancient volcano eruptions which caused lava to flow into large basins. Molten lava was able to seep upwards near the edges of the Maria

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39
Q

How were Terrae formed?

A

Terrae are the lighter parts of the Moon and called the Lunar Highlands. They are composed of Feldspar, which is lighter in colour than the Maria as it has crystallised slower, and also reflects more of the Sun’s light

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40
Q

How are Craters formed?

A

The Lunar Craters were formed from collisions with asteroids and meteorites on the surface. As the Moon has no atmosphere, there is no protection from incoming missiles

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41
Q

How were the Lunar Mountains formed?

A

Nearer the edges of the Maria, the mountain ranges were thrust upwards, forming mountains

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42
Q

How are Lunar Valleys formed?

A

Lunar Valleys form in between the mountains

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43
Q

How long is the Moon’s orbit of the Earth?

A

27.3 days

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44
Q

How long does it take for the Moon to rotate on its axis?

A

27.3 days

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45
Q

Why can we only see one side of the Moon?

A

The Moon is tidally locked with the Earth

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46
Q

How much of the Moon can we observe at one time?

A

59%

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47
Q

Why can we see more than 50% of the Moon?

A

Lunar Libration

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48
Q

What is up-to-down libration?

A

Libration Latitude

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49
Q

What is left-to-right libration?

A

Libration Longitude

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50
Q

How is the Moon’s Far side different from the Near side?

A

The Far side is devoid of Maria

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51
Q

How does Libration in Latitude occur?

A

The Moon’s equator is inclined to the plane of its orbit around the Earth by 1.5°; the plane of the Moon’s orbit is inclined at 5.1° to the ecliptic; this makes the Moon appear very high in the sky which is Libration in Latitude

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52
Q

How does Libration in Longitude occur?

A

Libration in Longitude occurs from the Moon’s varying speed in its elliptical orbit around Earth

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53
Q

What is an Apogee?

A

The point in the orbit of the moon or of an artificial satellite most distant from the centre of the Earth

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54
Q

What is a Perigee?

A

The point nearest the earth’s centre in the orbit of the moon or a satellite

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55
Q

What is the Moon’s mean diameter?

A

3,500 km

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56
Q

What is the Terminator?

A

The Terminator is the line that separates light and darkness on the moon

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57
Q

At which times during an eclipse can we see Bailey’s beads?

A

Second and Third contact

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58
Q

What scale is used to quantify the colour of a lunar eclipse?

A

Danjon Scale

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59
Q

How long does it take for the Moon to rotate an angle of 240 Degrees?

A

18 days

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60
Q

Where are the Apennine Mountains located?

A

The Apennine mountains are located between the Sea Of Serenity and the Sea of Rains

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61
Q

Why does Libration in Longitude occur?

A

During the Moon’s orbit, the orbital speed changes due to its elliptical orbit. The Moon’s rotation remains constant. This allows the eastern and western limb to be visible during different times of the lunar month

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62
Q

Which are older: Maria or Highlands?

A

Highlands

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63
Q

How can you deduce that the Highlands are older than the Maria?

A

The Maria have less craters in them suggesting they are younger as they aren’t old enough to have many craters from old impacts

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64
Q

Why is it best to observe craters near the Terminator?

A

There is a high contrast around the area which creates exaggerated shadows

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65
Q

How much is the Moon inclined to its orbit by?

A

The Moon’s equator is inclined to the plane of its orbit around the Earth by 1.5 Degrees

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66
Q

How much is the Moon’s orbit inclined to the ecliptic?

A

The plane of the Moon’s orbit is inclined at 5.1 Degrees to the ecliptic

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67
Q

What is tidal locking?

A

Tidal locking is when a satellite’s orbital period exactly matches its rotational period. An example is the Moon. Only one side of the Moon ever faces the Earth

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68
Q

What are the theories regarding the origin of the Moon?

A
  1. Giant Impact Hypothesis
  2. Fission Theory
  3. Capture Theory
  4. Co-Accretion Theory
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69
Q

Why do the phases of the Moon occur?

A

The phases of the Moon occur because the Moon is always 50% illuminated and 50% in darkness.
When the Moon orbits around the Earth, the angle we view the Moon from changes so we see different amounts of light and dark sides of the Moon

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70
Q

What is the Giant Impact Hypothesis?

A

A large astronomical body (named Theia) struck Earth and the debris cooled and condensed to become the Moon

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71
Q

What is the Fission Theory?

A

The Earth was spinning so quickly, a part of Earth broke off and formed the Moon

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72
Q

What is the Capture Theory?

A

The Earth and Moon were formed at different places in the Solar System but the Earth captured the Moon with the Earth’s gravitational force

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73
Q

What is the Co-Accretion Theory?

A

The Co-Accretion theory is the theory that the Earth and the Moon formed together at the same time out of material from a solar nebula

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74
Q

Why is the Giant Impact Hypothesis the most accepted theory regarding the origin of the Moon?

A

The Giant Impact Hypothesis is supported by the Moon’s lack of substances that evaporate (volatiles), the discovery of KREEP-rich rocks on Moon and its small iron core

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75
Q

Why can we see many rings on a during an eclipse?

A

When a large light source casts a shadow of a small object, it results in a dark central shadow with a surrounding lighter shadow

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76
Q

What is a ‘Blood Moon’?

A

A ‘Blood Moon’ is when the Moon appears to turn red during a lunar eclipse

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77
Q

Why does the ‘Blood Moon’ occur?

A

When the Moon is completely blocked by the Earth, no light directly reaches the Moon’s surface.
The only light that reaches the surface of the Moon, are the rays that have been refracted from the Earth’s atmosphere and red rays have the longest wavelengths so refract the most and are able to be bent so much that the rays hit the Moon. Therefore, the Moon appears red

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78
Q

What happens during the First Umbral Contact of a lunar eclipse?

A

This is the time when the Moon first enters the Earth’s Penumbra

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79
Q

What happens during the Second Umbral Contact of a lunar eclipse?

A

This is the time when the Moon is completely in the Umbra

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80
Q

What happens during the Third Umbral Contact of a lunar eclipse?

A

This is the time when the Moon first starts to exit the Earth’s Umbra

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81
Q

What happens during the Fourth Umbral Contact of a lunar eclipse?

A

This is the time when the Moon exits the the Earth’s Penumbra

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82
Q

What are Baily’s beads?

A

Small bright spots of Sunlight before and after totality which are caused by the Sun’s rays shining through the valleys on the Moon

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83
Q

What is the diamond ring effect?

A

When only one of Baily’s beads is visible

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84
Q

Why does the Moon look as if it’s the same size as the Sun?

A

The Moon and the Sun both roughly have angular diameters of 0.5 Degrees

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85
Q

What is Gravitational High Tide?

A

Gravitational High Tide is when the Moon’s gravity makes the Earth’s water bulge so it is a high tide when you are facing the Moon

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86
Q

What is Inertial High Tide?

A

Inertial High tide is when the water that isn’t pulled by the Moon, becomes flung outwards by the spinning Earth

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87
Q

When is there a low tide?

A

When the Earth spins away from the high tide

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88
Q

What is Lunar tide?

A

When the tides are controlled by the Moon’s gravity

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89
Q

How do tidal forces occur?

A

The inverse square nature of the force causes the gravitational pull of the larger object on the smaller object’s nearer side to be greater than that of its far side. This is equivalent to two equal and opposite forces acting on the near and far sides that tend to stretch and elongate the smaller object.
The smaller object also causes a similar, but weaker force on the larger object

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90
Q

How do tidal forces affect the Earth-Moon system?

A

The Moon exerts tidal forces onto the Earth causing tidal bulges in the oceans on the parts of the Earth facing towards and away from the Moon

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91
Q

How many times does the coast experience high or low tides?

A

There are two daily high and low tides

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92
Q

What are Lunar tides?

A

Tides caused by the Moon

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93
Q

What are Solar tides?

A

Tides caused by the Sun

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94
Q

What are Neap tides?

A

‘Low’ high tides

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95
Q

What are spring tides?

A

‘High’ high tides

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96
Q

When can spring tides occur?

A

Spring tides can only occur when the moon is in the full or new phase

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97
Q

Why do spring tides occur?

A

The positions of the Solar and Lunar tides add up

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98
Q

When can neap tides occur?

A

Neap tides can only occur during quarter moons

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99
Q

Why do neap tides occur?

A

Neap tides occur as the solar tide adds to the lunar low tide, which partially cancels it out

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100
Q

What is another consequence of tidal forces?

A

Precession

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101
Q

What is precession?

A

Precession is the change in the orientation of the rotational axis of a rotating body

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102
Q

What is the evidence of precession?

A
  1. The changing ‘Pole Star’
  2. The changing locations of the equinox: these are drifting westwards. For example, the First Point of Aries that is used to mark the spring equinox but this is now in Pisces
  3. The misalignment of ancient monuments and temples
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103
Q

What is a total solar eclipse?

A

When the Moon passes directly in front of the Sun , it obscures light for observers and produces a dark shadow

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104
Q

What is the Umbra?

A

The area during a Solar eclipse where the Sun is fully covered by the Moon

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105
Q

What is the Penumbra?

A

The area of observation where the Sun is partially covered

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106
Q

What are Baily’s beads?

A

Baily’s beads are when the Sun’s rays shine through the valleys of the Moon and are visible

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107
Q

What is the diamond ring effect?

A

The diamond ring effect is when only one Baily bead is visible

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108
Q

What is the First Umbral Contact for a solar eclipse?

A

When the Moon first touches the Sun

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109
Q

What is the Second Umbral Contact for a solar eclipse?

A

The Moon is just about to fully cover the Sun

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110
Q

What is the Third Umbral Contact for a solar eclipse?

A

The Moon has just finished covering the Sun

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111
Q

What is the Fourth Umbral Contact for a solar eclipse?

A

The Moon is just about to exits the Sun’s Umbra

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112
Q

What is an Annular eclipse?

A

An annular eclipse is when the Moon’s silhouette is slightly smaller than an normal eclipse and a ‘ring of fire’ occurs as the Moon is in its apogee in its elliptical orbit around Earth

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113
Q

When do lunar eclipses occur?

A

Lunar eclipses occur when the Moon passes through the Earth’s shadow

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114
Q

What happens during a lunar eclipse?

A

During a lunar eclipse at totality, the Moon appears red in colour due to predominantly red light refracting through the Earth’s atmosphere and illuminating the Moon

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115
Q

What is the First Umbral Contact for a lunar eclipse?

A

When the Moon first enters the Earth’s Penumbra

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116
Q

What is the Second Umbral Contact for a lunar eclipse?

A

The Second Umbral Contact is when the Moon is completely in the Umbra of the Earth

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117
Q

What is the Third Umbral Contact for a lunar eclipse?

A

When the Moon first exits the Umbra

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118
Q

What is the Fourth Umbral Contact for a lunar eclipse?

A

When the Moon completely exits the Penumbra

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119
Q

Who calculated the average circumference of the Moon?

A

Eratosthenes

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120
Q

How did Eratosthenes calculate the circumference of the Earth?

A

He read that at noon on the Summer Solstice, columns of temples did not cast any shadows in Syene (Tropic of Cancer).
At the same time in Alexandria, the Sun’s position was about 7° (roughly one 50th of a circle) from the zenith.
He knew that the distance from Syene to Alexandria was 790 km and used simple Geometry to work out that the circumference of the Earth was 50 x this.
He worked this out to be 39,500 km. His reading was very accurate as it was in 5% of the actual circumference of the Earth

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121
Q

What assumptions did Aristarchus to calculate the Moon’s diameter?

A

He determined:
1. A lunar eclipse was produced when the Moon passed into the Earth’s Umbra
2. The Sun was so far away that its rays were parallel when reaching the Earth
3. The Moon’s path took it through the centre of the Earth’s Umbra which has the same diameter of the Earth

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122
Q

How did Aristarchus calculate the ratio of the Moon’s diameter: the Earth’s diameter?

A

Using his three assumptions, Aristarchus showed that:
diameter of Moon . .Time interval from U1 to U2
————————– = —————————————
diameter of Earth . . Time interval from U2 to U4

He calculated the Moon’s diameter was between 0.32 and 0.40 times of the Earth’s. The correct value is 0.27

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123
Q

What did Archistarchus measure to deduce the distance to the moon?

A

The width of his thumbnail

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124
Q

What did Eratosthenes use to measure the circumference of the Earth?

A

Lengths of Shadows at local noon

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125
Q

What did Eratosthenes use to measure the distance to the Sun?

A

The angle between the Sun and Moon at half-moon

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126
Q

What did Archistarchus use to measure the diameter of the moon?

A

Timings of Umbral Contacts during total lunar eclipse

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127
Q

What did Eratosthenes do to calculate the diameter of the Sun?

A

He compared the apparent angular sizes of the Moon and the Sun

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128
Q

What does one year correspond to?

A

One year corresponds to one complete orbit of the Earth around the Sun

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129
Q

What is one sidereal day?

A

One sidereal day is the time it takes for the Earth to spin once on its axis: 23 h 56 min

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130
Q

What is one solar or synodic day?

A

The time it takes for the Earth to spin so the Sun appears in the same place in the sky: 24 h 00 min

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131
Q

How long is one Sidereal Month?

A

27.3 days

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132
Q

How is a Sidereal Month measured?

A

The time it takes for the Moon to complete one revolution of the Earth

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133
Q

How long is one solar (Synodic) month?

A

29.5 days

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134
Q

Why is a Synodic month longer than a Sidereal Month?

A

During the time it takes for the Moon to complete one orbit of the Earth, The Earth has moved through an angle of 27° in its orbit around the Sun. This is why the Moon needs an extra 2.2 days to re-align with the Sun and Earth again

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135
Q

What do Sundials indicate (timing)?

A

Sundials indicate Apparent Solar Time (AST)

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136
Q

What is Apparent Solar Time?

A

Apparent Solar Time is the apparent timing of the Sun seen by an observer. This is in reference to the actual position of the Sun in the Sky

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137
Q

What do ordinary time-keeping devices indicate (timing)?

A

Mean Solar Time (MST)

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138
Q

What is Mean Solar Time?

A

Mean Solar Time is the time calculated by the mean time it takes for the Sun to cross the sky each day in a consistent manner

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139
Q

What is Equation of Time (EOT)?

A

Equation of Time is the difference between mean solar time and apparent solar time, which varies with the time of year. It is used to correct Mean Solar Time to the Apparent Solar Time

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140
Q

What is the Sun’s ‘speed’ when the EOT is positive?

A

The real Sun is ‘fast’

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141
Q

What is the Sun’s speed when the EOT is negative?

A

The real Sun is ‘slow’

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142
Q

What can a shadow stick determine?

A

A shadow stick can determine at which time the Sun culminates and also the observer’s longitude

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143
Q

How do you calculate Equation of Time?

A

Equation Of Time= Apparent Solar Time-Mean Solar Time

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144
Q

What is an analemma?

A

An analemma is a chart showing how the EOT varies with the Sun’s declination during the course of one year

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145
Q

What does an analemma chart look like?

A

An analemma is likened to a ‘snowman’ with a bigger bottom than top

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146
Q

How does the Earth’s orbit vary the EOT (Equation Of Time)?

A

The Earth travels at different speeds in its orbit which causes the real Sun to move slower faster or slower in the sky on different dates

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147
Q

How does the tilt of the Earth vary the EOT (Equation Of Time)?

A

When it is close to the solstices, the real Sun is travelling faster from East to West than when close to the equinoxes when a large component of its apparent motion is northwards or southwards; the Sun therefore lags behind and leaps ahead of the Mean Sun in the East-West motion

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148
Q

How do you calculate the EOT (Equation Of Time)?

A

EOT = AST - MST

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149
Q

What is Retrograde motion?

A

Retrograde motion is when the planets occasionally appeared to travel backwards from east to west in a ‘loop-the-loop’ motion

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150
Q

How can you explain Retrograde motion?

A

Retrograde motion is the faster moving Earth overtaking the superior planet on the inside of its orbit

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151
Q

What is the Zodiacal Band?

A

The band that contains all the orbits of the planets and the Sun. The band is at ~8° either side of the ecliptic due to the large orbital inclination of Mercury

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152
Q

What is an inferior planet?

A

An inferior planet is a planet that has an orbit that is smaller than the other planet in perspective

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153
Q

What is a superior planet?

A

A superior planet is a planet that has an orbit that is greater than the other planet in perspective

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154
Q

What is Inferior conjunction?

A

Inferior conjunction is when an inferior planet is in between your planet and the Sun in perspective

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155
Q

What is Superior conjunction?

A

Superior planet is when an inferior planet and your planet are on the opposite sides of the Sun

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156
Q

What is greatest elongation?

A

Greatest elongation is when an inferior planet appears furthest away from the Sun

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157
Q

What is opposition?

A

Opposition is when a superior planet is opposite to the Sun. The superior planet is closest to Earth and at its brightest

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158
Q

What is the transit of a planet?

A

A transit is when a planet goes in front of the Sun

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159
Q

What is an occultation?

A

An occultation is when a planet obscures a distant star as it goes in front of it for a few moments

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160
Q

What are the equatorial coordinates of the First Point Point of Libra?

A

RA = 12h 00min
Dec. = 0°

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161
Q

Which space probe studied Halley’s comet?

A

Giotto

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162
Q

What is another word for solar prominence?

A

A solar flare

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163
Q

What is a Transit?

A

A transit is when a planet and the Earth line up so that the planet appears to move across the Sun

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164
Q

What is an occultation?

A

An occultation is when one body in space obstructs our view of another. Transits and eclipses are types of occultations

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165
Q

What is Opposition?

A

When a superior planet is closest to the Earth and in the opposite section of the sky compared to the Sun

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166
Q

What is Conjunction?

A

When to celestial bodies appear to have a close approach and look as if they overlap

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167
Q

What is Greatest Elongation?

A

Greatest elongation is when an inferior planet appears to be the furthest distance away from the Sun. It occurs when the Planet is at a 90° angle to the Earth and the Sun

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168
Q

Why are we able to see more meteors during a meteor shower?

A

A meteor shower occurs when the Earth passes through a meteor stream. The meteor stream consists of many small grains of dust and rock which become very hot through friction with the Earth’s atmosphere

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169
Q

Which two stars does Orion’s Belt point to?

A

Sirius and Aldebaran

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170
Q

Why do different cultures have different names for constellations?

A

When asterisms and constellations were first named, there was very little communication. Different cultures were relatively isolated compared with today, and so were unable to share/exchange stories, myths and legends.
Different cultures were able to see different stars and identify patterns because of different geographical locations.
Different cultures used different stories, myths and legends on which many of their asterisms and constellations were named

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171
Q

What has a declination of 0°?

A

The Celestial Equator

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172
Q

What would an object be if it had a constant brightness then disappeared before it reached the horizon?

A

An artificial satellite

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173
Q

What would an object most likely be if it has coloured lights and a white light that flashes at regular intervals?

A

An Aircraft

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174
Q

What makes planets visible?

A

Reflection

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175
Q

What allows the radar technique to determine distances to nearby objects?

A

Reflection

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176
Q

What causes the dust tail of a comet to be visible?

A

Reflection of sunlight

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177
Q

Why does the dust tail of a comet point away from the Sun?

A

Radiation pressure from the Sun

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178
Q

What causes the ion tail of a comet to be visible?

A

Fluorescence / excitation of ions

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179
Q

Why does the ion tail of a comet point away from the Sun?

A

Interaction with Solar wind

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180
Q

How many constellations are there?

A

88 constellations

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181
Q

What are asterisms?

A

Asterisms are unofficial, popular patterns of bright stars that have a close likeness to their name. Examples include ‘The Plough’ in Ursa Major or Orion’s Belt

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182
Q

What is an open cluster of stars? (Give an Example)

A

A group of stars that are roughly the same age and formed in the same giant molecular cloud. An example is the Pleiades

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183
Q

What are constellation pointers? (Give an Example)

A

Pointes from constellations that point to another star or celestial object. An example is The Plough which points to Polaris and the ‘handle’ arc to Arcturus

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184
Q

What is an optical double star?

A

Two stars that appear to have merged from our perspective

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185
Q

What is declination?

A

Declination is the projection of latitude onto the celestial sphere; it is measured in degrees (+&-signs indicate N or S)

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186
Q

What is Right Ascension?

A

Right Ascension is the East-to-West coordinate system. Right ascension is measured from the first point of Aries; it is measured in hours and minutes where 1 hr=15° and 1 min=0.25°

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187
Q

What is Azimuth?

A

The Azimuth is a bearing from due north moving round eastwards to the point on the observer’s horizon directly under the star; it ranges from 0° to 360° back to 0° again

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188
Q

What is Zenith and Nadir?

A

The Zenith is the point directly above the observer
The Nadir is the point directly below the observer

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189
Q

What is your Meridian?

A

Your Meridian is the great arc passing through the celestial poles, as well as the zenith and nadir of an observer’s location

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190
Q

What is Diurnal Motion?

A

Diurnal motion is when a star reaches its highest point (culminate) when they are due south as they cross the observer’s meridian and later set in the west

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191
Q

How long does it take for the Earth to rotate once?

A

23hrs 56 mins

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192
Q

What is a Sidereal day?

A

A sidereal day is how long it takes for the Earth to rotate in accordance with the stars

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193
Q

What is a Solar Day?

A

A Solar Day is the time it takes for the Earth to rotate around its axis so the Sun appears in the same position in the sky

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194
Q

How long is a Solar Day?

A

24 hrs

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195
Q

Why does a Solar day occur?

A

A Solar day occurs because, during the time it takes for the Earth to rotate 360°, the Earth also moves around the Sun by 1° so it needs to rotate for a further 4 mins to align back to the same point as the Sun

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196
Q

How can you tell the local sidereal time (LST) using Right Ascension?

A

Local Sidereal time is the time the Right Ascension of a star that lies on the observer’s meridian at a given moment in time. An example is if a star with RA= 14 h 45 mins lies on an observers meridian, the LST is 14:45

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197
Q

What is a star’s hour angle?

A

A star’s hour angle is the time since the celestial object was last crossing the observers meridian
or
the angular distance on the celestial sphere measured westward along the celestial equator from the meridian to the hour circle passing through a point

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198
Q

How do you calculate a star’s hour angle?

A

Hour Angle = Local Sidereal Time - Right Ascension

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199
Q

What does the Hour Angle tell you?

A

If the Hour Angle is negative, its value tells an astronomer how long it will take before the star or celestial object will be crossing their meridian

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200
Q

What is the NCP?

A

The NCP is the North Celestial Pole. It is the equivalent of a North Pole in the celestial sphere. Polaris is located within 0.8° of the NCP

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201
Q

What is Altitude?

A

The Altitude of a star measures the angle between the horizon, you, and the celestial object

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202
Q

What is the Celestial Equator?

A

The Celestial Equator is the hypothetical sphere which contains the stars ‘painted’ on the inside

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203
Q

What is the Ecliptic?

A

The Ecliptic is an imaginary circle on the Celestial Sphere that represents the apparent path of the Sun during the year

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204
Q

How can you work out the observer’s latitude?

A

Altitude of NCP (or SCP) = observer’s latitude
Altitude of Polaris = observer’s latitude

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205
Q

What is Polar Distance?

A

Polar Distance is the angular distance of a star from the NCP

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206
Q

How do you work out Polar Distance?

A

Polar Distance = 90° - Declination

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207
Q

How can you also figure out polar distance?

A

The small circle that a star traces out during a sidereal day has a radius equal to its polar distance

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208
Q

What is Upper Transit?

A

When a celestial body passes your meridian at its highest point. The Upper Transit is when a star culminates

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209
Q

What is Lower Transit?

A

Lower transit is when a celestial body passes your meridian at its lowest point

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210
Q

How can you calculate altitude?

A

Altitude = Latitude ± Polar Distance
at upper and lower transits

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211
Q

What are Circumpolar Stars?

A

Circumpolar stars are stars the remain visible at all times and do not set below the horizon

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212
Q

How can you determine if a star is circumpolar?

A

For a star to be circumpolar:
90° - Declination < latitude of the observer

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213
Q

What does Orion’s belt point to?

A

Towards the left, it points to Sirius. To the right, it points to Aldebaran then the Pleiades

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214
Q

What does the Square Of Pegasus point to?

A

It points to the Andromeda Galaxy and Fomalhaut

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215
Q

How can you describe a meteor when viewed?

A

A short, bright streak of light in the sky, lasting a few seconds

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216
Q

What do nebulae look like when observed?

A

A fuzzy patch of light

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217
Q

What does the aurora look like to the naked eye?

A

A curtain or stream of of coloured light

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218
Q

Why would greatest elongation be the best position to observe an inferior planet?

A

The angle between the planet and the Sun is large. This means the planet is in a darker area of sky so contrast is greater

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219
Q

What is the diameter of the Milky Way galaxy?

A

30 kpc

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220
Q

Name seven types of galaxies:

A

Elliptical
Barred Spiral
Spiral
Lenticular
Peculiar
Dwarf Elliptical
Quasar

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221
Q

What are binary stars?

A

2 stars the orbit around the mutual centre of gravity

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222
Q

What is a double star?

A

2 stars that appear as one when viewed

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223
Q

What are variable stars?

A

Stars that change brightness

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224
Q

Name 4 reasons why its difficult to view the sky:

A
  1. We’re restricted to view only at night
  2. The atmosphere continuously rises and falls; this causes the stars to ‘twinkle’
  3. Skyglow; an orange haze cast by lights near urban places
  4. ‘Glare’ from lights that ruins our dark adaption
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225
Q

What are the Van Allen Belts?

A

The Van Allen belts are regions with intense radiation.
The Inner belt consists of high energy protons.
The Outer belts are high energy electrons that dip toward the poles

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226
Q

How do you calculate your latitude?

A

Measure the angle from your zenith to the Sun.
Add the angle from your zenith to the Sun at the equator for this specific day

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227
Q

What are seasonal constellations?

A

Seasonal constellations are the Constellations that can only be seen in certain times of the year as the Sun blocks us from viewing them when the Sun covers it up

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228
Q

What is Precession?

A

Precession is the circular motion of the axis of something that is rotating

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229
Q

Why do some ancient monuments seem random?

A

The current celestial alignments differ from the original alignments of the monuments because the Earth’s axis of rotation isn’t fixed; it precesses

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230
Q

What were the ancient models of the Solar System?

A

Aristotle and Plato models suggested a geocentric system with the Earth at the centre of the Solar System

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231
Q

What were the issues with the Geocentric system?

A

The Geocentric system had an inability to explain the observed retrograde motion of the planets

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232
Q

How was the geocentric system developed to explain retrograde motion?

A

Each planet was placed on a small rotating circle (an epicycle) whose centre revolved around the Earth on another circle (the deferent)

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233
Q

How did Ptolemy adjust the epicycle system?

A

Ptolemy put the Earth slightly off-centred and an imaginary point called the Equant from which the angular motion of the centre of each epicycle was uniform

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234
Q

What is the Heliocentric system?

A

The Heliocentric system is a model that suggested the Sun was at the centre of the solar system

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235
Q

Who was the first person to suggest a Heliocentric system?

A

Archistarchus of Samos argued for a Heliocentric system in c.270 BCE based on his calculations that the Sun was much larger than the Earth
However, the theory was only recognized as a real hypothesis from Nicholas Copernicus who applied mathematical modelling

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236
Q

What did Galileo Galilei do in 1609?

A

Galileo used the first telescope to observe the sky. He provided evidence for the Heliocentric theory:
1. The apparent size of the Planet Venus changed and showed phases
2. Four Moons that orbited Jupiter

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237
Q

What is Kepler’s first law of planetary motion?

A

The first law of planetary motion states that planets move in elliptical orbits around the Sun, with the Sun at one focus of ellipse (the other is empty). The points in the orbit at which is closest and furthest from the Sun are called the Perihelion and aphelion

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238
Q

What is Kepler’s second law of planetary motion?

A

Kepler’s second law states that an imaginary line from the Sun to a planet sweeps out equal area in equal intervals in time

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239
Q

What is Kepler’s third law?

A

Kepler’s third law states that the square of the orbital period (T) of a planet is proportional to the cube of its mean distance (r) from the Sun

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240
Q

How can you write Kepler’s third law mathematically?

A

T² α r³ or t²
. . . . . . . . — = a constant
. . . . . . . . r³

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241
Q

What is Newton’s law of Universal Gravitation?

A

Newton’s law of Gravitation states that every body in the Universe attracts every other body with a force that is directly proportional to the product of their masses and inversely proportional to the square of their distance apart

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242
Q

What is the inverse square law?

A

The inverse square law states that the intensity of gravitational force is inversely proportional to the square of the distance from the source

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243
Q

What is the Perigee?

A

The closest point in a satellite’s orbit of the Earth (it is at its fastest here)

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244
Q

What is the Apogee?

A

The furthest point in a satellite’s orbit of the Earth (it is at its slowest here)

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245
Q

What is the Perihelion?

A

The closest point in an astronomical bodies’ orbit of the Sun (it is at its quickest here)

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246
Q

What is the Aphelion?

A

The furthest point in an astronomical bodies’ orbit of the Sun (it is at its slowest here)

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247
Q

What is the inverse equation for force and distance?

A

F α 1
. . —
. . d²
F = force
d = distance

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248
Q

What is the mean thickness of the crust on the Moon?

A

The mean thickness of the Lunar crust is 50-60 km, which is 3 times that of the Earth’s

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249
Q

How is the Far Side of the Moon different to the Near side?

A

The thickness in the lunar highlands on the far side can be as large as 160 km whereas, the Near side has lunar maria which is lower land

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250
Q

How is the Moon’s core different to the Earth’s?

A

The radius of the Moon’s core is less than 25% of the Moon’s radius. In comparison, the Earth’s core extends to more than 50% of its radius

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251
Q

Why is the Moon’s core ‘weird’?

A

The Moon’s core is offset from the centre by about 2 km

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252
Q

What spacecraft first took pictures of the Moon’s far side?

A

The Luna 3 of Russia took the first picture of the Moon’s far side

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253
Q

What year did the Luna 3 probe take the pictures of the far side?

A

1959

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254
Q

What were the Apollo missions?

A

The Apollo missions were a series of US-planned missions which aimed at sending the first man on the Moon

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255
Q

What Apollo successfully sent a man on the Moon?

A

Apollo 11

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256
Q

Name four theories regarding the origin of the Moon:

A
  1. Giant Impact Hypothesis
  2. Fission Theory
  3. Capture Theory
  4. Co-accretion Theory
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257
Q

What is the Giant Impact Hypothesis?

A

The Giant Impact Hypothesis suggests that a large astronomical body - astronomers name Theia - stuck the Earth. Theia was vaporised and the debris cooled and condensed to form the Moon. This also suggests why the Earth is at a tilt of 23.5°. It also is supported by the fact the Moon has little volatiles and its small iron core

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258
Q

What is the Fission Theory?

A

The Earth was spinning so rapidly part of it spun off and formed the Moon

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259
Q

What is the Capture Theory?

A

The Capture Theory suggests that the Earth and the Moon were formed in different places in the Solar System, but the Earth caught captured the Moon with its gravitational force

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260
Q

What is the Co-Accretion Theory?

A

The Co-Accretion theory suggests the Earth and the Moon formed at the same time out of material from the Solar Nebula

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261
Q

How many astronomers walked on the surface of the Moon?

A

12

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262
Q

What instruments were left on the Moon?

A

A retro-reflector
A seismometer
A solar wind particle collector

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263
Q

What was the last Apollo mission?

A

Apollo 17

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264
Q

How is the Far side of the Moon different to the Near Side?

A

It has a thicker crust
It contains more craters
Almost devoid maria

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265
Q

How can you safely observe the Sun?

A

Pinhole projection
H-alpha filter
Telescopic projection

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266
Q

What are sunspots?

A

Sunspots are cooler areas of the Photosphere where the Sun’s magnetic field rises from below the Sun’s surface and the magnetic regions poke through. They are darker in colour as they are expending less energy and have a lower temperature

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267
Q

What is the average temperature of a Sunspot?

A

Umbra is ~3800K
Penumbra is ~5600K

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268
Q

How can you calculate solar rotation period?

A

If the difference in longitude (ΔL) of a sunspot occurs in a time interval, then rotation period (T) can be calculated by:
T . . 360°
—- = ——
Δt . . ΔL

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269
Q

What is the earliest Nuclear Fusion?

A

The earliest Nuclear Fusion is when hydrogen (H) nuclei fuse into Helium (He) nuclei

270
Q

Why can Nuclear Fusion only happen in the Sun’s core?

A

The temperature has to be high enough to overcome the mutual electrostatic repulsion of the positively-charged nuclei

271
Q

What is the chain of reaction that happens in the Sun?

A

The Proton-Proton or Deuterium-Deuterium chain

272
Q

What happens in each stage in the proton-proton chain?

A

At each stage in the chain, mass (m) is lost and converted into energy (E). This is in accordance with Einstein’s equation E=mc², where c is the speed of light

273
Q

How much mass does the Sun lose?

A

The Sun loses 4 million tonnes of mass every second, this is insignificant as the Sun’s total mass is 2.0 × 10²⁷ tonnes

274
Q

What is the zone above the Sun’s core?

A

Radiative zone

275
Q

What happens in the radiative zone?

A

This zone is where the energy in the form of photons (gamma-radiation) is transferred in a random manner due to the scattering of photons by electrons outwards

276
Q

What is the zone outside the radiative zone?

A

The convection zone

277
Q

How thick is the convection zone?

A

~200 000 km

278
Q

What happens in the convection zone?

A

The convection zone is where the thermal energy is transported to the photosphere by rising convection currents of hot plasma

279
Q

What is at the top of the convection zone?

A

The photosphere

280
Q

How hot is the photosphere?

A

The photosphere is ~2 million K at the base. At the visible part of the photosphere, the temperature is 5800 K

281
Q

How thick is the photosphere?

A

100 km

282
Q

How does the Sun radiate energy?

A

The Sun radiates energy in the form of visible light but also to a lesser extent of infra-red, ultra-violet and X-Radiation

283
Q

What are the 2 parts of the Sun’s atmosphere?

A

The chromosphere and corona

284
Q

How thick is the chromosphere?

A

2000 km thick

285
Q

How hot is the chromosphere?

A

400 K - 100 000 K at the top

286
Q

How hot is the corona?

A

2 million K

287
Q

How far can the corona extend?

A

The corona can extend outwards for millions of km into space

288
Q

What is ‘slow’ solar wind?

A

An outflow of charged particles (mostly protons and electrons)

289
Q

Where does ‘slow’ solar wind come from?

A

The Corona

290
Q

What is the speed of ‘slow’ solar wind?

A

~400 km/s

291
Q

Where does ‘fast’ solar wind originate from?

A

Coronal holes

292
Q

What is ‘fast’ solar wind associated with?

A

Coronal mass ejections and Solar Flares

293
Q

What is solar wind responsible for?

A

Solar wind is responsible for aurora and the creation of cometary tails

294
Q

What is the Butterfly Diagram?

A

The butterfly diagram is a diagram that shows the solar cycle of sunspots. The cycle begins with a few spots at mid latitude. The numbers of sunspots fall and rises, and they drift towards the solar equator

295
Q

How long does the solar cycle last?

A

11 years

296
Q

What is a Type II Supernova?

A

A Red Supergiant collapses

297
Q

What is a Type Ia Supernova?

A

A Type Ia Supernova occurs when Red Giant star is in a binary system with a white dwarf. Over time, the white dwarf will gravitationally steal matter from the Red Giant, resulting in the increase of mass. It will surpass the Chandrasekhar limit and the electron degeneracy pressure will be insignificant in preventing the collapse, resulting in a supernova

298
Q

What stage of a star does a planetary nebula represent?

A

Death

299
Q

What is Fast solar wind?

A

A build up of of magnetic energy which is released from a sunspot

300
Q

What is slow solar wind?

A

Particles that are emitted from all over the Sun.
They are slowed by the magnetic fields of the Sun
They are mostly charged protons and electrons

301
Q

When is there more fast solar wind?

A

During the middle of a Sunspot cycle where there are the most amount of Sunspots

302
Q

Why does Nuclear fusion only take place in the Sun’s core?

A

The particles need to be hot enough to withstand the electric repulsive forces. They have to hit each other fast so they need to be at very high pressure (15 Million Kelvin)

303
Q

What are sunspots?

A

Sunspots are black spots on the surface of the Sun that are formed where the the magnetic field leaves the surface. It is a cool area where no convection occurs

304
Q

What prevents the ionising rays from reaching the surface of the Earth?

A

Magnetosphere

305
Q

What is the equation that tells you how to find longitude in the UK?

A

Local Mean Time - Mean Solar Time In Greenwich
_______________________________________
. . . . . . . . . . . . . . . . . . . . . . . 4
=Degrees of Longitude to the East

306
Q

What is the First Umbral Contact for a solar eclipse?

A

The First Umbral Contact is when the Moon starts to cover the Sun

307
Q

What is the Second Umbral Contact for a solar eclipse?

A

The second Umbral contact is when the Moon has just finished covering the Sun

308
Q

What is the Third Umbral contact for a solar eclipse?

A

The Moon is on the cusp of leaving the Umbra of the Sun

309
Q

What is the Fourth Umbral Contact for a solar eclipse?

A

The fourth Umbral Contact is when the Moon has just left the Sun

310
Q

What is an Annular solar eclipse?

A

When the Moon is too small to fully cover the Sun so a ring of light surround the Sun

311
Q

Why does an Annular Solar eclipse occur?

A

An Annual Solar Eclipse occurs when the Moon’s orbit is in an apogee and the the Moon appears too small to cover the entire Sun compared to normal eclipses

312
Q

What is an accretion disk?

A

An accretion disk consists of hot, swirling gas captured by a white dwarf ( or neutron star or black hole ) from a binary companion star

313
Q

When can white dwarf supernova occur?

A

A white dwarf supernova can occur only in a binary system, and all such events are thought to have the same luminosity

314
Q

What are the Sun’s internal divisions in order?

A

Photosphere
Convective zone
Radiative zone
Core

315
Q

How does a H-alpha filter make the observation of the Sun safe?

A

A H-alpha filter makes the observation of the Sun safe as the intensity of light received from the Sun is reduced

316
Q

Where does the Sun rotate faster?

A

The Sun rotates faster at the equator then the poles

317
Q

How hot is the Corona?

A

2 million K

318
Q

How hot is the Core of the Sun?

A

15 million K

319
Q

How hot is the photosphere?

A

5800 K

320
Q

How hot is the top of the Chromosphere?

A

100 000 K

321
Q

How hot is a typical Sunspot Umbra?

A

3800 K

322
Q

How hot is a typical Sunspot Penumbra?

A

5600 K

323
Q

What are the planets in our Solar System? (IN ORDER STARTING CLOSEST TO THE SUN)

A

Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune

324
Q

What are the four terrestrial planets?

A

Mercury
Venus
Earth
Mars

325
Q

What are the similarities between the terrestrial planets?

A

They are all relatively small rocks surrounding iron cores

326
Q

What are the four gaseous giant planets?

A

Jupiter
Saturn
Uranus
Neptune

327
Q

What are the similarities between the gaseous planets?

A

The gaseous planets have liquid interiors and substantial atmospheres of hydrogen and Helium with traces of methane and ammonia. They also have complex ring systems and large amounts of Moons

328
Q

What are the planets that have rings?

A

Jupiter
Saturn
Uranus
Neptune

329
Q

Why aren’t dwarf planets considered planets?

A

They lack the gravitational force needed to sweep debris out of their orbit.
They also don’t consistently stay in the zodiacal band

330
Q

Where are the dwarf planets found?

A

All the dwarf planets (except Ceres) are found in the Kuiper belt

331
Q

Where is Ceres found?

A

Ceres is found in the Asteroid belt

332
Q

What are the 4 notable dwarf planets?

A

Ceres, Pluto, Eris and Makemake

333
Q

What are SSSO’s?

A

Small Solar System Objects which include asteroids, meteoroids and comets

334
Q

Where are most asteroids found?

A

Most Asteroids are found in the Asteroid Main Belt between the orbits of Mars and Jupiter

335
Q

How big are asteroids?

A

Asteroids range from ~10 m to ~1000 km; most have irregular shapes

336
Q

Where do Short-term comets originate from?

A

Kuiper Belt

337
Q

What is the life period of a short-term comet?

A

< 200 years

338
Q

Why do some short-term comets go into elliptical solar orbits?

A

The gravitational influence of Neptune nudge the comets into solar orbits; these have a subset period of < 20 years

339
Q

Where do Long-period comets originate from?

A

Oort Cloud, a spherical distribution of icy bodies about halfway to the nearest star

340
Q

What is the life period of a long-term comet?

A

> 200 years

341
Q

How do long-period comets differ from short-period ones? (3 WAYS)

A
  1. They have unpredictable orbits
  2. Highly-inclined to the plane of the Solar System
  3. Some orbiting in the opposite sense to that of the planets
342
Q

What happens as the comet approaches the Sun?

A

Rarefied gasses and dust envelop the nucleus of dust and ice; eventually, one or more tails develop that can be several million kilometres long

343
Q

What happens as the comet moves away from the Sun?

A

The tail and the comet become less visible. The comet ceases to be influenced by solar radiation, fades from view and returns to the outer Solar System

344
Q

Describe a comet’s ion tail

A

A comet’s ion tail is long, straight and predominantly blue in colour

345
Q

What are Meteoroids?

A

Meteoroids are particles of dust, rock and mixtures of stone, ice and metal that are in orbit around the Sun

346
Q

What happens when a meteoroid enters the Earth’s atmosphere?

A

When a particle enters the Earth’s atmosphere, air resistance converts kinetic energy into thermal energy, heating the particles. This results in a streak of light visible in the night sky that is called a shooting star or meteor

347
Q

What is a meteor shower?

A

A Meteor Shower is when the Earth passes through a meteoroid stream in the wake of a comet, many more meteors are visible

348
Q

What is the radiant?

A

The radiant is the point where the individual meteors appear to diverge from a vanishing point. This is simply due to perspective. The shower is named after the nearest constellation

349
Q

What are Fireballs?

A

Fireballs are when larger meteoroids enter the atmosphere and produce bright light. These survive their journey, reaching the Earth’s surface as meteorites

350
Q

What is AU?

A

AU is an astronomical unit that is equal to the mean distance from the Earth to the Sun. 1 AU = 150 million km

351
Q

What are the two types of a telescope?

A

Refractors and Reflectors

352
Q

What is the job of the Objective element?

A

The job of the Objective element is to collect as much light as possible and focus the light to a small bright image

353
Q

What does the eyepiece of a telescope do?

A

The eyepiece magnifies the image of the objective element so the images can be observed in a higher resolution and are much brighter

354
Q

What is a telescope’s aperture?

A

The telescope’s aperture is the size of the hole that light goes through

355
Q

How does the telescope’s aperture affect the telescope? (GIVE 2 EFFECTS)

A

The more light enters the telescope, making images brighter
The higher amount of detail that can be resolved

356
Q

What does resolution depend on?

A

The resolution depends on the wavelength of light entering the telescope: the longer the wavelength, the poorer the resolution. So, red nebulae are not as good as that in blue nebulae surround young stars

357
Q

What is a telescope’s light grasp?

A

The light grasp is a measure of how much light is captured by the objective element; this depends on the cross-sectional area. The area depends on the square of the diameter of the objective lens or mirror.
light grasp α area α (diameter of the objective element)²

358
Q

What does magnification depend on?

A

Magnification depends on the ratio of focal length of the objective (fo) and eyepiece (fe)

359
Q

How do you calculate magnification?

A

magnification = focal length of objective = fo
. . . . . . . . . . . . . ————————————- . .—
. . . . . . . . . . . . . focal length of eyepiece . . fe

360
Q

How can you increase the magnification of a telescope?

A

The shorter focal length, the greater the magnification

361
Q

What is a Barlow lens?

A

A Barlow Lens allows eyepieces to be slotted into it. The optical elements of a Barlow lens increase the magnification by a factor of 2 or 3

362
Q

What is Field of View (FOV)?

A

Field of View of a telescope is the circle of sky that is visible through its eyepiece

363
Q

What is Field of View (FOV)?

A

Field of View of a telescope is the circle of sky that is visible through its eyepiece

364
Q

What is Field of View measured in?

A

Field of View is measured in degrees or minutes of arc (arcmins) where 1°=60’

365
Q

Why do astronomers prefer to use reflector telescopes?

A

Astronomers prefer to use reflector telescopes as they can have larger objective apertures that can be supported by the telescope. Also, it is possible for mirrors to reflect light with almost no loss in intensity or chromatic abberation

366
Q

What is chromatic aberration?

A

Chromatic Aberration is when lenses tend to focus different wavelengths of light to slightly different points. This causes images to be blurred and unclear

367
Q

What are the problems with Refractor telescopes?

A

Chromatic Aberration
- Long in size which makes viewing impractical

368
Q

What are the 4 main types of space probes?

A
  1. Fly-by Missions
  2. Orbiters
  3. Impactors
  4. Landers
369
Q

What are fly-by missions? (Give an example)

A

Fly-by missions are missions that analyse and explores many targets, without getting caught in the gravitational pull of the target. Missions include 𝘝𝘰𝘺𝘢𝘨𝘦𝘳𝘴 𝘐 and 𝘐𝘐 (that visited the outer planets) and 𝘕𝘦𝘸 𝘏𝘰𝘳𝘪𝘻𝘰𝘯𝘴 (that explored Pluto and the outer Solar System)

370
Q

What are orbiter missions? (Give an example)

A

Orbiter missions are probes that get caught in the gravitational fields of the target. Missions include the 𝘔𝘢𝘨𝘦𝘭𝘭𝘢𝘯 probe that mapped the planet Venus using radar, 𝘋𝘢𝘸𝘯 (that made detailed studies of asteroids Ceres and Vesta) and 𝘑𝘶𝘯𝘰 that measured Jupiter’s composition and magnetosphere

371
Q

What are Impactor missions?

A

Impactor missions are missions that are planned to crash onto a target to create an artificial quake. Examples include the third stages of 𝘚𝘢𝘵𝘶𝘳𝘯 𝘝 spaceship that were impacted onto the lunar surface to cause artificial moonquakes and the 𝘋𝘦𝘦𝘱 𝘐𝘮𝘱𝘢𝘤𝘵 probe which crashed on Comet Temple 1 to study the internal composition of a comet

372
Q

What are lander missions?

A

Missions where the impact is controlled and the probe touches down intact on the surface. Example include 𝘏𝘶𝘺𝘨𝘦𝘯𝘴 landing on Saturn’s moon Titan, the 𝘚𝘱𝘪𝘳𝘪𝘵 and 𝘖𝘱𝘱𝘰𝘳𝘵𝘶𝘯𝘪𝘵𝘺 on Mars and 𝘗𝘩𝘪𝘭𝘢𝘦 onto the comet 67P/Chunyumov-Gerasimenko in order to perform a chemical analysis of its water content

373
Q

Why can we see a Comet’s ion tail?

A

A comet’s ion tail consists of charged ions that have been excited by the particles in the solar wind and emit light by fluorescence when they de-excite

374
Q

What is a stationary point?

A

A stationary point is when a planet’s motion changes direction

375
Q

What is a Protoplanetary disc?

A

A Protoplanetary disc is a rotating disk of dense gas and dust surrounding a newly formed star

376
Q

What is a frost line?

A

A frost line marked the boundary beyond which it was cold enough for volatiles to freeze onto tiny particles of dust; within the frost line, only metals and rock could condense into solid grains

377
Q

How did the planets form?

A

Accretion

378
Q

What is accretion?

A

Accretion is when small grains of solid material collide and stick into each other forming larger flakes. These collide into other pieces forming larger and larger bodies

379
Q

How long did it take before the accreted pieces formed the cores of planets?

A

After ~100 million years, the accumulated pieces formed the metallic and silicate cores of the planets

380
Q

What happened to the bodies beyond the frost line?

A

Beyond the frost lines, the cores of the protoplanets grew to much bigger sizes due to the large abundance of ices. The gravitational attraction of these massive cores were able to draw in large amounts of hydrogen and helium that were present in the outer solar system to form the atmospheres of four gas giant planets

381
Q

What factors affect the presence of an atmosphere? (GIVE 3 FACTORS)

A
  1. A planet’s or moon’s mass
  2. Temperature
  3. Magnetic Field
382
Q

How does temperature affect the presence of an atmosphere?

A

The hotter the temperature, the faster the gas molecules move, making them more likely to escape the gravitational attraction of the planet or moon

383
Q

How does a planet’s mass affect the presence of an atmosphere?

A

The greater the mass, the greater the gravitational pull on the atmosphere

384
Q

How many bodies were there estimated to be in the early solar system?

A

50 bodies

385
Q

Why are there only 8 bodies currently in the Solar System?

A

The 50 bodies collided, broke apart and re-formed a significant number of times before becoming an ordered system with stable orbits around the Sun

386
Q

How is Mercury evidence for previous collisions?

A

Mercury’s iron core occupies over 60% of its volume; the planet is thought to have lost most of its rocky interior due to a collision with a protoplanet about one sixth of its size

387
Q

How does axis tilts provide evidence for previous collisions?

A

The backwards spin of Venus and sideways spin of Uranus suggests that these two planets had significant collisions during the Solar System’s history

388
Q

What is tidal heating?

A

Tidal heating is when internal friction and the interior of a Moon becomes warm

389
Q

What happens during tidal heating?

A

Thermal energy is produced at the expense of rotational kinetic energy, and the moon’s spins slows down a little. Over time, this results in a synchronised rotation where the Moon’s rotational and orbital period are the same

390
Q

How is energy transferred during tidal heating?

A

The Internal friction produces energy which heats up the moon

391
Q

What happens when the moon’s rotation becomes synchronised with it’s orbit?

A

Tidal heating doesn’t end because most moon orbits aren’t perfectly circular: A varying orbital speed means that tidal bulges still occur and oscillate about a mean position

392
Q

What is the orbital interaction between various bodies called?

A

Orbital Resonance

393
Q

How does orbital resonance work?

A

Orbital Resonance works when the different moons are aligned and and ‘tugged’ out of shape meaning they don’t have circular orbits

394
Q

What is tidal heating responsible for?

A

Tidal heating is responsible for the molten layers that are beneath the rocky or icy crusts of large moons. This is responsible for active volcanoes or cryovolcanoes (ice volcanoes)

395
Q

What happens if a moon’s elastic forces aren’t strong enough?

A

If a moon’s internal elastic forces that resist deformation aren’t strong enough, the tidal forces will break up the body or prevent one from forming

396
Q

How are planetary rings formed?

A

Planetary rings are believed to be formed after a moon was broken up by tidal forces and the fragments spread around the planet

397
Q

What is the Roche Limit?

A

The Roche limit is the minimum distance a large satellite can approach its parent body without being torn apart

398
Q

What are the Lagrangian points?

A

The Lagrangian points are the stable positions near large objects in orbit. These are the points where a small object is able to orbit

399
Q

How can a Satellite be stable in the Lagrangian points?

A

The Lagrangian points in a two body system (an example is the Earth and Sun) at which their combined force of gravity is equal to the centripetal force needed to maintain the circular motion of a third object (a satellite)

400
Q

What are Exoplanets?

A

Exoplanets are planets that orbit a star outside the Solar System

401
Q

What observation methods of stars can you use to discover exoplanets? (NAME 3)

A
  1. Astrometry
  2. Transit Method
  3. Radial Velocity Method
402
Q

What is Astrometry?

A

Astrometry is when massive Exoplanets orbit their star and their combined gravitational pull can cause the star to move or wobble slightly in its position around the common centre of gravity

403
Q

What is the Transit Method?

A

The Transit Method is when you can detect an Exoplanet transiting across the host star. This causes a very small (1%) drop in brightness for the duration of their transit

404
Q

What is the Radial Velocity Method?

A

The radial velocity method is when the slight wobbling of a star due to orbital motion of the exoplanet can be detected as small Doppler-shifts in the wavelengths of the the star’s spectral lines as it moves in the line-of-sight of the observer

405
Q

How do astronomers carry out the Radial Velocity method?

A

Astronomers uses spectroscopy to reveal small changes in a stars spectral lines

406
Q

What method is the most effective for detecting exoplanets?

A

The Radial Velocity Method

407
Q

What are the two chemicals that are essential for the creation of life?

A

Carbon and Water

408
Q

Why is Carbon essential for the creation of life?

A

Carbon has the ability to make interesting compounds such as amino acids and can form more complex organic molecules

409
Q

Why is Water essential for the creation of life?

A

Water in its liquid form is an excellent solvent and acts as a transport mechanism for many nutrients

410
Q

What is the Habitable (Goldilocks) Zone?

A

The Habitable Zone is the area a planet must be if liquid water is to be located on its surface

411
Q

What is the Drake Equation?

A

The Drake Equation is the equation that attempts to estimate the likelihood of intelligent life in our galaxy

412
Q

Which three moon’s in the solar system do astronomers believe could have primitive life?

A

Saturn’s Moon Titan
Jupiter’s moon Europa
Saturn’s moon Enceladus

413
Q

Why could Saturn’s moon Titan support life?

A

Saturn’s moon titan has seas of liquid hydrocarbons

414
Q

Why could Jupiter’s moon Europa support life?

A

Jupiter’s moon Europa contains an ocean of liquid water under its outer shell

415
Q

Why could Saturn’s moon Enceladus support life?

A

Saturn’s moon Enceladus has eruptions of salt water, hydrocarbons and carbon

416
Q

What does SETI stand for?

A

Search for Extraterrestrial Intelligence

417
Q

What types of waves are used for SETI?

A

Radio

418
Q

What are the factors of the Drake Equation? (HINT: THERE ARE 6)

A
  1. Number of Stars in our galaxy
  2. Number of earth-like planets in the Habitable zone
  3. Fraction of stars with orbiting planets
  4. Fraction of Earth-like planets on which life evolves
  5. Fraction of Planet’s life for which intelligent civilisations live
  6. Fraction of planets where life is intelligent and develops technology to communicate with us
419
Q

What are extremophiles?

A

Extremophiles are life forms that can live in extreme temperatures, conditions, high pressure and high concentrations of salt water

420
Q

How many exoplanets systems are currently known?

A

> 200

421
Q

How can you estimate the diameter of an exoplanet?

A

diameter = speed × time interval of beginning a transit to being fully in the disk of the parent star

422
Q

Which planet in the Solar System has the largest mass?

A

Jupiter

423
Q

Which planet in the Solar system has the lowest density?

A

Saturn

424
Q

Which Planet orbits closest to the Kuiper belt?

A

Neptune

425
Q

What is the approximate distance to the Oort Cloud?

A

2 l.y. (2 light years)

426
Q

What shape can the orbits of long-period comets be?

A

Elliptical and parabolic

427
Q

How could water have come to Earth?

A

Deposits by comets and large asteroids

428
Q

What are the classes of meteorites?

A

Iron
Stone
Stoney-Iron

429
Q

What are the two most common elements in an iron meteorite?

A

Iron and Nickel

430
Q

Where is it believed that iron meteorites originate?

A

The cores of asteroids

431
Q

What are the two most common elements in a stone meteorite?

A

Oxygen and Silicon

432
Q

Give examples of 5 large scale collisions in the Solar System

A
  1. Giant Impact Hypothesis which formed the Moon
  2. Uranus’ sideways spin
  3. Venus’ backwards spin
  4. Impact craters on the Moon, Mars and asteroids
  5. Large Iron Core of Mercury
433
Q

How are grooves formed on Mars’ moon Phobos?

A

Rocky Matter was ejected from Mars following a collision with a large meteoroid

434
Q

Which 2 Moons were caused by gravitational capture?

A

Mars’ Deimos and Phobos

435
Q

What are the causes of Mars’ lack of atmosphere?

A

After Mars’ formation, Mars probably has a molten core in which electric currents could flow and produce a magnetic field.
Mars’ magnetic field was able to deflect particles of solar wind around the planet.
As Mars cooled, its molten core solidified and currents could no longer flow meaning the Magnetic field was lost
The solar wind was no longer deflected so blew away particles in Mars’ atmosphere

436
Q

How is Enceladus responsible for Saturn’s E-ring?

A

Water and ice is ejected from Enceladus’ geysers. Some water and ice falls back onto Enceladus and some is captured by the gravitational field of Saturn forming its E-ring

437
Q

What is the smallest astronomical body in the Solar system that is spherical?

A

Mimas (One of Saturn’s moon)

438
Q

What are the opposing factors that an astronomical object depends on to be spherical or not?

A

Gravitation and Elastic

439
Q

How can a moon be unaffected by tidal forces?

A

The moon could have a small diameter and/or the distance between the moon and its parent planet is large

440
Q

Why is it more likely for planets with large diameters to be broken up by Tidal forces when the come closer than a planet’s Roche Limit?

A

Tidal forces are gravitational in origin. Gravity follows an inverse square law.
The moon must have a large enough diameter for the difference in gravitational pull on the ‘near’ and ‘far’ side of the moon to be significant/greater than elastic forces

441
Q

Why do the Gas giants have larger cores compared to the rocky planets?

A

For our Solar System, the Frost Line was about 5 AU from the Sun. Within the frost line, volatile ices were unable to condense due to the high temperatures. However, beyond the Frost Line, it was cold enough for ices to condense and these are thought to have caused the significantly larger cores of the gas giants

442
Q

Why is there an absence of hydrogen and helium in the Inner Solar System compared to the Outer Solar system and gas giants?

A

Solar wind is most likely reason for ‘blowing’ light gases toward the Outer Solar system.
Solar wind is ‘strongest’ closer to the Sun i.e. in the inner Solar System

443
Q

What is magnitude?

A

Magnitude is the measure of a brightness of a star

444
Q

What is the scale of magnitude?

A

The magnitude difference of 1 corresponds to the fifth root of 100≈2.5

445
Q

What is apparent magnitude?

A

Apparent magnitude is how bright a star seems from Earth

446
Q

What factors affect apparent magnitude? (GIVE 4 FACTORS)

A
  1. The total energy by the star in the visible region
  2. The distance to the star
  3. The amount of interstellar gas and dust that reflects and absorbs light
  4. The amount of light absorbed and scattered by the Earth’s atmosphere
447
Q

What is absolute magnitude?

A

Absolute magnitude is how bright a star would be if all stars are 10 parsecs away

448
Q

How do you calculate absolute magnitude?

A

M=m+5- 5log(d)
M=absolute magnitude
m=apparent magnitude

449
Q

How do astronomers find the chemical makeup of a star?

A

Spectroscopy

450
Q

What is spectroscopy?

A

Spectroscopy is when you collect light with the aid of a telescope and then diffract it to create a spectrum

451
Q

How do you know what chemicals are in a star?

A

When you do a spectroscope, there are a set of darker lines. The spectral lines correspond to exact wavelengths at which atoms in the outer layers of stars absorb light; each element has its own unique set of wavelengths

452
Q

What do astronomers classify stars in?

A

Spectral types

453
Q

How do astronomers classify spectral types?

A

Astronomers examine the ratios of

hydrogen: helium: other elements

454
Q

What are the different Spectral Types?

A

O B A F G K M

455
Q

What is the H-R Diagram?

A

The H-R diagram is a scatter graph the classify’s stars in accordance to their luminosity, spectral type, colour, temperature and evolutionary stage

456
Q

What is plotted against each other on a H-R Diagram?

A

A star’s luminosity or absolute magnitude is plotted against either spectral type or temperature

457
Q

Where are the main sequence stars found on the H-R Diagram?

A

The main sequence stars lie in a band running from top left to bottom right

458
Q

Where are Giants and Supergiants found on the H-R Diagram?

A

Giants and Supergiants stars lie above the main sequence band

459
Q

Giants are what colour?

A

Red or Blue

460
Q

Where are White dwarf stars found on the H-R diagram?

A

White dwarfs lie below the main sequence band towards the left

461
Q

How long is one light year?

A

1 l.y = 9.5 × 10 ¹²

462
Q

How long is one parsec?

A

1 pc = 3.1 × 10 ¹³

463
Q

How long is one parsec in accordance to light years?

A

1 pc = 3.26 l.y

464
Q

What are minutes of arc?

A

Minutes of Arc is one degree split into 60 minutes of arc. 1 arc minute is further split into arc seconds where one degree is 3600 arc seconds

465
Q

What technique can we use to figure out the distance to a near star?

A

Heliocentric Parallax

466
Q

What is Parallax?

A

Parallax is when the position of a near object differs greater in comparison to distant objects when viewed from different places

467
Q

What are variable stars?

A

Variable stars are stars that vary in brightness

468
Q

Why do stars appear to vary in brightness? (GIVE 2 REASONS)

A
  1. Changing physical quantity such as size
  2. Changes in the light reaching Earth
469
Q

What are light curves?

A

Graphs of apparent magnitude against time

470
Q

What are the two types of variable stars?

A

Intrinsic and Extrinsic variables

471
Q

What are Cephied Variables?

A

Cephied Variables are when the Star actually pulsates. When it’s larger, it has a greater magnitude, and therefore it’s brighter

472
Q

What are binary stars?

A

Binary stars are when there is a bright primary star and a dimmer secondary star that orbit around their mutual centre of gravity

473
Q

What happens when the secondary star eclipses (moves in front of) the primary star?

A

When the secondary eclipses the primary, there is a large drop in intensity

474
Q

What happens when the primary star eclipses the secondary star?

A

When the primary star eclipses the secondary star, there is a small drop in intensity

475
Q

How do radio telescopes work?

A

Radio telescopes consist of a large concave dish that reflects and focuses radio waves into an antenna. Here, the antenna converts the radio waves into electrical signals that can be stored and processed

476
Q

Why are radio telescopes built large?

A

Radio telescopes are large so they can achieve the best possible resolution by collecting as much radio waves as possible

477
Q

What is Aperture Synthesis?

A

Aperture synthesis is when multiple telescopes are linked electronically to study the same source of radio waves. This converts many telescopes into one large one with an aperture equivalent to the largest distance between individual telescopes

478
Q

Why are most radio telescopes located on high mountains?

A

The air is dry and steady. Also, there is a lack of clouds which obscure your view

479
Q

Where is the optimum place to put a telescope?

A

Space

480
Q

Why is space the best place to put a telescope?

A

The satellite is above atmosphere where there is:
- no air to blur or absorb light
- no day-night cycle where your viewing times are restricted
- no light pollution from skyglow
meaning it is in the optimum position to place a telescope in space

481
Q

What are the disadvantages of having a satellite telescope?

A

Space telescopes have limited lifetimes, very difficult to construct, launch and maintain

482
Q

What discoveries were first made using radio waves? (NAME 6)

A
  1. Quasars
  2. The structure and rotation of our galaxy
  3. Pulsars
  4. Protoplanetary discs
  5. Jets from black holes
  6. SETI (Search for extraterrestrial intelligence)
483
Q

What discoveries were first made using Infrared (IR)? (NAME 3)

A
  1. Protostars
  2. Interstellar dust and molecular clouds
  3. ‘Hotspots’ on the moon
484
Q

What discoveries were first made using ultraviolet (UV)?

A

Corona and chromosphere structure of young stars

485
Q

What discoveries were first made using X-ray? (NAME 3)

A
  1. Active galaxies
  2. Accretion disks surrounding black holes
  3. Supernova remnants
486
Q

What discoveries were first made using gamma(γ) rays?

A

Gamma ray bursts in distance galaxies

487
Q

Where must other wavelengths observatories be put?

A

All wavelengths other than optical or radio, need to be put on fixed observing platforms orbiting the Earth. However, Infrared observatories can be sited on high mountains

488
Q

What is the distance modulus formula?

A

M = m + 5 - 5log(d)
M=absolute magnitude
m=apparent magnitude
d= distance

489
Q

How can you use Spectroscopy and the H-R diagram to determine distances to stars?

A

First, you obtain a spectrum of the star and determine its spectral class. Then, using the H-R diagram you get its absolute magnitude (you use the main sequence band). You then observe the star to get its apparent magnitude. Finally, you use the distance modulus formula to calculate 𝗱

490
Q

What are the first 5 letters in the greek alphabet?

A

α (alpha), β (beta), γ (gamma), δ (delta), ε (epsilon)

491
Q

What is light intensity proportional to?

A

light intensity is proportional to 1
. . . . . . . . . . . . . . . . . . . . . . . .————–
. . . . . . . . . . . . . . . . . . . . . . . .distance²

492
Q

How do calculate the ratio of light intensity of two stars?

A

intensity of light from α . (distance β)²
——————————— = ——————
intensity of light from β . (distance α)²

493
Q

What is plotted against what in a typical Hertzsprung-Russell diagram?

A

Luminosity against Spectral type

494
Q

How does temperature and absolute magnitude increase in a H-R diagram?

A

Temperature increases to the left and Absolute magnitude increases downwards

495
Q

What spectral type is the Sun?

A

G2

496
Q

How are absorption lines connected to the chemical composition of a star?

A

Light passing through the outer layers a star is made of all wavelengths / energy. Some of this light has the correct wavelength/energy to excite atoms in the star’s outer layers.
When the atoms de-excite they emit radiation/photons of the same wavelength/energy but in a random direction and not necessarily ‘outwards’. The wavelengths / energies at which these ‘reactions’ occur depends on the chemical element. Light received on Earth is dimmer and so darker at these wavelengths

497
Q

What is the intensity of light proportional to?

A

1 / d²

498
Q

What type of variable star is used by astronomers to determine distances to stars?

A

Cepheid variable

499
Q

What is a Cataclysmic variable star?

A

Cataclysmic variable stars are stars which irregularly increase in brightness by a large factor, then drop back down to a inactive state

500
Q

What is an example of Cataclysmic variable star?

A

Supernova

501
Q

Why is there variability in brightness for eclipsing binary stars?

A

For most of the time, the primary and secondary stars are not aligned. This is their constant brightness.
The larger/primary ‘dip’ in a light curve occurs when the
dimmer/secondary star is directly in front of the brighter/primary star.
The smaller/secondary ‘dip’ occurs when the secondary star is behind the primary star.
This time, the corresponding drop in intensity is not as significant

502
Q

What is SKA?

A

Square Kilometre Array

503
Q

What is aperture synthesis?

A

The process of linking multiple telescopes together to increase aperture size

504
Q

What is an impact of atmospheric refraction?

A

Stars near the horizon appear higher in the sky than they actually are

505
Q

Which part of a spectrometer splits up light from astronomical objects into a spectrum?

A

Diffraction grating

506
Q

Which types of nebulae expand?

A

Supernova remnants and Planetary Nebulae

507
Q

What is the Electromagnetic spectrum from shortest to longest wavelength?

A

Gamma
X-Ray
UV
Visible
IR
Microwave
Radio

508
Q

What are Nebulae?

A

Nebulae are large interstellar clouds of dust and gas

509
Q

What are open clusters?

A

Open clusters are a group of young stars that formed from the same giant molecular cloud. They all are roughly the same age

510
Q

What are Globular Clusters?

A

Globular clusters a group of older stars

511
Q

Where are open clusters found?

A

Open clusters are found on the spiral arms of the Galaxy

512
Q

Where are globular clusters found?

A

Globular clusters are found in a ‘halo’ around the centre of the galaxy

513
Q

What is the Messier Index?

A

The Messier Index is a catalogue of 110 astronomical objects that can be observed

514
Q

How are all stars first originally formed?

A

All stars originate from the gravitational collapse of of a cool, dense molecular cloud of gas and dust that are found in the spiral arms of galaxies. As the cloud collapses, it becomes unstable and fragments into smaller clumps (protostars) that will form the cores of individual stars

515
Q

What happens when a protostar collapses?

A

Gravitational potential energy is converted into kinetic energy and its temperature increases. It eventually becomes hot enough for the fusion of hydrogen into helium

516
Q

What is radiation pressure?

A

Radiation Pressure is the pressure that is exerted on a surface due to the exchange of momentum between an object and the electromagnetic field. The Radiation Pressure of stars is caused by the nuclear fusion of elements

517
Q

What happens during the main sequence stage?

A

During the main sequence stage, radiation pressure and gravity balance. This stops any further gravitational collapse

518
Q

How long is a star in the main sequence stage?

A

A star is in the main sequence stage for ~90% of its lifetime

519
Q

What is the Chandrasekhar Limit?

A

The Chandrasekhar Limit is the maximum mass of a stable white dwarf

520
Q

What is the accepted figure for the Chandrasekhar limit?

A

The maximum limit is a Sun with a core 1.4 times the mass of the Sun

521
Q

How is a Red Giant formed?

A

When the generation of energy stops, the radiation pressure becomes zero and the star gravitationally collapses. This raises the temperature of the star and causes the fusion of hydrogen again but this time in a shell around the core. The helium core further contracts which increases the rate of energy generated. This makes the star expand and form a Red Giant

522
Q

What happens if a Red Giant’s core becomes extremely hot?

A

If the core becomes hot enough, helium will fuse into carbon

523
Q

What are Planetary Nebula?

A

A planetary nebula is a nebula that is formed by an expanding shell of gas from an ageing star

524
Q

Why does the core of a star eventually stop collapsing?

A

Electron Degeneracy Pressure

525
Q

What is Electron Degeneracy Pressure?

A

Electron Degeneracy Pressure is because the electrons cannot be squeezed together any closer and so resist any further compression

526
Q

What is formed after the Red Giant?

A

A White Dwarf

527
Q

What occurs after a White Dwarf?

A

A Black Dwarf

528
Q

Why do Black dwarfs form?

A

Black Dwarfs form after a white dwarf cools down and loses its energy

529
Q

What happens if a star has a core mass greater than the Chandrasekhar limit?

A

If a star has a core mass greater than the Chandrasekhar limit, the star will continue to collapse and will be able to fuse carbon into Neon. Fusion continues until iron is formed in the core

530
Q

What will happen if the core’s mass is greater than the Chandrasekhar limit but has a core mass less than 3x the mass of the Sun?

A

The collapse is stopped by the neutron degeneracy pressure

531
Q

What is the neutron degeneracy pressure?

A

The electrons are forced into protons to form a solid core of neutrons, and these neutrons prevent being compressed further

532
Q

What happens after the halt of collapse of a star due to the neutron degeneracy pressure?

A

The star becomes a neutron star

533
Q

What will happen if the core’s mass is greater than the Chandrasekhar limit and has a core mass greater than 3x the mass of the Sun?

A

The Star will turn into a red Supergiant after it is a main sequence. The neutron degeneracy pressure is insufficient to prevent the gravitational collapse after the supernova and the core collapses further to form a black hole

534
Q

What are Emission Nebulae?

A

An emission nebula is a cloud of ionized gas. The most common source for ionizations are high energy photons emitted from a nearby star

535
Q

What are Reflection nebulae?

A

Reflection Nebulae are clouds of dust which are simply reflecting the light of a nearby star or stars. The nearby star or stars are not hot enough to cause ionization in the gas of the nebula like in emission nebulae but are bright enough to give sufficient scattering to make the dust visible

536
Q

What are Absorption nebulae?

A

Absorption nebulae are nebulae that can be seen because they obscure, or absorb, the light coming from stars or bright nebulae behind them

537
Q

What is Averted vision?

A

Averted vision means looking slightly to the side of a faint, extended object so that light falls onto the rods (not the cones) of the eye’s retina
In dark conditions, the cones (which lie where the optical axis joins the retina) are not sensitised, but the rods (which lie adjacent to the optical axis) are

538
Q

Which British astronomer published the Caldwell Catalogue?

A

Sir Patrick Moore

539
Q

What are diffraction spikes?

A

Diffraction spikes are when some stars appear to have crosses through them

540
Q

Which might initiate the collapse of a giant gas cloud that may eventually form stars?

A

Gravitational Waves and Supernovae

541
Q

What prevents the gravitational collapse of a white dwarf star?

A

Electron degeneracy Pressure

542
Q

How would you describe the main sequence stars that are at the bottom right on the H-R diagram as?

A

Old and Dim

543
Q

How would you describe the main sequence stars that are at the top left on the H-R diagram as?

A

Young and bright

544
Q

Why are neutron stars and black holes not found on the H-R diagram?

A

Neither emits enough radiation to be ‘bright’ enough to register on the luminosity/absolute magnitude/vertical axis

545
Q

What is our Galaxy called?

A

Milky Way

546
Q

What is Milky Way in Latin?

A

Via Lactea

547
Q

How far is the Sun from the centre of our Galaxy?

A

~10 kpc

548
Q

What is the radius of our Galaxy?

A

~15 kpc

549
Q

What type of galaxy is the Milky Way?

A

Barred Spiral Galaxy

550
Q

Where are open clusters of young stars found?

A

In the Spiral Arms

551
Q

Why can’t we see the centre of the Galaxy using visible light?

A

The Centre of the Galaxy is blocked by dust and dense gas

552
Q

What is the Doppler Principle?

A

The Doppler Principle is that relative motion changes the frequency or wavelength of observed waves. We notice this change mainly with sound waves

553
Q

What does it mean if the observed wavelength is longer than it should be?

A

The object is moving away from us

554
Q

What does it mean if the observed wavelength is shorter than it should be?

A

The source is moving towards us

555
Q

What can the Doppler Shifts tell us about the Milky Way?

A

The received wavelengths are supposed to be 21 cm, but they aren’t exactly. This will tell us the relative velocities of the different parts of the Milky Way and how it’s rotating

556
Q

What is redshift?

A

Redshift is receding sources of waves

557
Q

What is blueshift?

A

Blueshift refers to sources that are approaching us

558
Q

What is the used system for the classification of Galaxies?

A

Hubble Classification System

559
Q

What is the diagram that classifies galaxies?

A

Tuning Fork Diagram

560
Q

How many theories are there regarding the formation of galaxies?

A

2

561
Q

What is the theory on the formation of galaxies from gas?

A

Vast clouds of gas and dust collapsed gravitationally, allowing stars to form

562
Q

What is the theory on the formation of galaxies from lumps of matter?

A

Lumps of matter were already present in the Universe. They clumped together under their mutual gravitational attraction to form galaxies

563
Q

What type of galaxy is believed to be the earliest type?

A

Elliptical

564
Q

What are ‘active galaxies’?

A

Active galaxies are galaxies that have a small core of emission in a normal galaxy. It emits huge amounts of radiation in wavebands such as X-ray and radio regions

565
Q

What is an Active Galactic Nucleus (AGN)?

A

An Active Galactic Nucleus is a compact region at the centre of a galaxy that have a much higher luminosity over a portion of the electromagnetic spectrum which indicates that the luminosity isn’t produced by stars

566
Q

What are Seyfert galaxies?

A

Seyfert Galaxies are galaxies that have a bright nucleus and emit strongly in the IR, UV and X-ray regions

567
Q

Who discovered Seyfert galaxies?

A

Seyfert galaxies were discovered by Carl Seyfert in 1943

568
Q

What are Quasars?

A

A quasar is an extremely luminous AGN that emits strongly in the UV and X-ray regions

569
Q

What do Quasars appear like?

A

Quasars appear star-like on images and have large redshifts

570
Q

What are BL Lacertae Objects (Blazars)?

A

Blazars are compact quasars where the galactic jets are pointing towards us

571
Q

What is the approximate size of the Local Group?

A

3 Mpc

572
Q

Name five galaxies our local group:

A

Any five of:
Andromeda Galaxy
Large Magellanic Cloud
Small Magellanic Cloud
Triangulum Galaxy
Milky Way
Pegasus Dwarf
etc.

573
Q

Which cluster is the Milky way in?

A

Virgo Cluster

574
Q

Which supercluster is the virgo cluster in?

A

Laniakea Supercluster

575
Q

What is Redshift?

A

Redshift is when objects moving away from us, are shifted towards the red end of the spectrum and the wavelengths of spectral lines become longer than the same corresponding wavelengths measured in a laboratory on Earth. It is an example of the Doppler Principle

576
Q

What is the equation to calculate the change in wavelength?

A

λ - λ₀ . .v
——- = –
. .λ₀ . . .c
λ = Observed wavelength
λ₀ = True Wavelength
v = Velocity
c = Speed of light

577
Q

Write out the Hubble’s Law

A

v = H₀d
H₀ = Hubble’s Constant
v = Velocity
d = Distance

578
Q

How can you determine the value of H₀?

A

Calculate the gradient of a v-d graph

579
Q

What is the value of Hubble’s Constant (H₀)?

A

The accepted value is 68 km/s/Mpc

580
Q

What is the Big Bang?

A

The Big Bang is a rapid expansion from an extremely high density to create the universe

581
Q

What is the Steady State Model?

A

The Steady State Model suggests that the the Universe always has been expanding. The density of the Universe is constant over time with new matter being constantly created

582
Q

What is a Cyclic Universe?

A

A Cyclic Universe suggests that there have been a series of Big Bang/ Big Crunch scenarios and will continue in the future

583
Q

Which two theories state that overall density decreases with time?

A

Big Bang and Cyclic models

584
Q

Which evidence supports the Big Bang model?

A

Quasars
Cosmic Microwave Background (CMB) Radiation
Hubble Deep Field (HDF) image

585
Q

How do Quasars support the Big Bang model?

A

Quasars are only found with high redshifts, which implies that they lie great distances from us and were created when the Universe was very young; the fact that quasars were more common in the early Universe compared with today which supports the nature of the Big Bang model

586
Q

How do Cosmic Microwave Background (CMB) radiation support the Big Bang model?

A

Russian cosmologist George Gamow predicted if the early Universe was hot and dense, it would’ve cooled and expanded to a temperature just above absolute zero. In 1965, Robert Wilson accidentally discovered CMB radiation from all parts of the sky that corresponded to a temperature of 2.7 K

587
Q

How does the Hubble Deep Field image support the Big Bang model?

A

These images were a series of long exposure images of empty space with a small field-of-view of 2.6 arcmins but the image revealed thousands of distant old galaxies, implying that the early Universe was very different from how it appears today

588
Q

What are the three possible models for the expanding Universe?

A
  1. Decelerating Universe
  2. Coasting Universe
  3. Accelerating Universe
589
Q

What does a decelerating Universe lead to?

A

A decelerating Universe leads to a collapse in a ‘Big Crunch’

590
Q

What does a coasting Universe lead to?

A

A coasting Universe will continue to expand at a constant rate

591
Q

If the expansion of the universe is Accelerating, what is fueling the expansion?

A

The expansion of the Universe is accelerating due to dark energy, a mysterious repulsive force, which increases the rate of expansion

592
Q

How much of the Universe is believed to be made up of dark matter?

A

25%

593
Q

Dark matter is used to explain what?

A

Gravitational Lensing

594
Q

What is Gravitational Lensing?

A

Gravitational Lensing is the apparent bending of light from galaxies to form multiple images of the same galaxy

595
Q

What is believed to be a form of black matter?

A

WIMPs (Weakly Interacting Massive Particles)

596
Q

What is the relationship between velocity and distance?

A

Velocity and Distance are directly proportional to each other

597
Q

How do you calculate recession velocity of a galaxy?

A

c(Δλ)
——– = v
. .λ
c = speed of light
Δλ = Change in wavelength
λ = Actual Wavelength
v = Recession velocity

598
Q

What is blueshift?

A

Blueshift is when light is shifted towards the shorter end of the spectrum, indicating that it is moving towards us

599
Q

What is the Equant?

A

The Equant is a mathematical concept used to explain observed speed changes in planetary orbit in a geocentric system

600
Q

What is an Epicycle?

A

The Epicycle is a geometric model that was used to explain the apparent change in speed and direction of the apparent motion of the planets. It was used in particular to explain retrograde motion

601
Q

What is the most appropriate united for distances to galaxies?

A

Megaparsec

602
Q

Why can the Hubble Constant given as an inverse of time?

A

The basic unit is the kilometre per second per megaparsec. The kilometre and megaparsec are both units of distance/length. These can effectively cancel to leave the unit as the ‘per second’

603
Q

What is Hubble Time?

A

Hubble time is the time for which the Universe has been expanding

604
Q

What are the approximate percentages of normal matter, dark matter and dark energy?

A

Normal matter - 5%
Dark Matter - 25%
Dark Energy - 70%

605
Q

What is Hubble Time?

A

The age of the Universe - 14 billion years

606
Q

What is Hubble length?

A

Hubble length is the length of the observable Universe

607
Q

Write out the Proton Proton chain?

A

1H+1H →2H+0e+0v
1 . . 1 . . . .1. . . 1 . . .0
2H+1H→3He
1 . . .1 . . . 2
3He+3He→4He+1H+1H
2. . . .2 . . . . 2 . . . 1 . . 1

608
Q

What is 0 e?

. . . . . . . 1

A

Positron

609
Q

What is 0 v?

. . . . . . .0

A

Neutrino

610
Q

What is Nicolaus Copernicus known for?

A

In 1543, Copernicus formulated the Heliocentric system, with the Sun at the centre rather than the Earth

611
Q

What is Tycho Brahe best known for?

A

In 1572, Brahe discovered a supernova in Cassiopeia

612
Q

What is Hans Lippershey known for?

A

In 1608, Lippershey invented the telescope

613
Q

What is Galileo Galilei known for?

A

In 1609, Galileo discovered the 4 Jovian moons, the Moon’s craters and the Milky Way Galaxy

614
Q

What is Johannes Kepler known for?

A

In 1609, Kepler announced the first and second laws of planetary motion.
He announced the third law in 1619

615
Q

What is Kepler’s First Law (The Law Of Orbits)?

A

The first law states that planets move in elliptical orbits around the Sun at one focus of each ellipse (the other is empty)

616
Q

What is Kepler’s Second Law (The Law Of Areas)?

A

Kepler’s second law states that an imaginary line from the Sun to a planet sweeps out equal areas in equal intervals of time

617
Q

What is Kepler’s Third Law (The Law Of Periods)?

A

Kepler’s third law states that the square of the orbital period (T) of a planet is proportional to the cube of its mean distance (r) from the Sun
T²
— = A constant
r³
or t²=r³

618
Q

What is Giovanni Cassini known for?

A

In 1666, Cassini noticed the Martian Polar Ice Caps

619
Q

What is Isaac Newton known for?

A

In 1668, Newton built the first reflecting telescope. In 1687, he published The Theory Of Universal Gravitation

620
Q

What did Isaac Newton discover?

A

Newton discovered that the force of weight is directly proportional to the product of the masses of the two objects

621
Q

What is Newton’s inverse law?

A

Newton found that the strength of gravity follows an inverse square law, this means that the strength of gravity goes down by the increase of distance squared
F×d²=k
F = Force (Newtons) d= Distance (metres) K= a constant

622
Q

What is Edmond Halley known for?

A

In 1705, Halley computed the orbit of the eponymous Halley’s Comet using Newton’s laws

623
Q

What is Charles Messier known for?

A

In 1781, Charles Messier published an astronomical catalogue consisting of nebulae and star clusters that came to be known as 110 ‘Messier objects’

624
Q

What is Christian Doppler best known for?

A

In 1842, Doppler discovered the ‘Doppler effect’ of moving stars

625
Q

What is Albert Einstein known for?

A

In 1905, Albert Einstein came up with the Theory Of Relativity in ‘On The Electrodynamics Of Moving Bodies’.
In 1916, he introduced the General Theory of Relativity

626
Q

What are Hertzsprung and Russel known for?

A

During 1911-14, they introduced the H-R Diagram that shows how the characteristics of stars are related

627
Q

What is the main band running through the H-R Diagram called?

A

The main sequence band

628
Q

What is the Bayer System?

A

The Bayer system uses Greek letters to represent relative magnitudes

629
Q

What is a spectroscope?

A

A spectroscope is a device for producing and recording spectra for examination

630
Q

What are the different uses for a spectroscope? (AND LIST THE 4 PROPERTIES OF STARS WHICH CAN BE INVESTIGATED)

A

Astronomers use spectroscopes to investigate the following properties of stars:

Chemical composition
Temperature
Radial Velocity
Stellar Classification (OBAFGKM)

631
Q

What did Edmond Halley do regarding astronomical units?

A

Edmond Halley devised a method of determining the size of an Astronomical Unit by observing transits of Venus

632
Q

What did transit observations determine?

A

A transit observations enabled the absolute size of the Solar system to be determined

633
Q

What are the two basic telescopes?

A

Reflectors and refractors

634
Q

What type of lens does a refracting telescope use?

A

Convex Lens

635
Q

What type of lens does a reflecting telescope use?

A

Parabolic (Concave) Lens

636
Q

What does an objective element do?

A

It collects as much light as possible and focuses it into a small, bright image

637
Q

What does an eyepiece lens do?

A

An eyepiece lens magnifies the image given by the objective element so we can see an image in high resolution

638
Q

What are the differences with a larger telescope? (ANSWER NAMES 2)

A
  1. More light enters the telescope; making the image brighter
  2. There is a higher resolution and a bigger amount of detail
639
Q

What does the resolution depend on (in terms of wavelengths)?

A

The wavelength of light that is entering the telescope; a red nebulae has a lower resolution compared to a blue nebulae as red has a longer wavelength

640
Q

What determines a telescope’s magnification?

A

The ratio of the lengths of the objective and and eyepiece

641
Q

What is the equation for magnification?

A

. . . . . . . . . . . . . . .focal length of objective. . . fo
magnification = ———————————– = —-
. . . . . . . . . . . . . . .focal length of eyepiece. . . fe

642
Q

Name two ways you can get greater magnification

A
  1. Use eyepieces of different focal lengths; the shorter the focal length, the greater the magnification
  2. Use a Barlow Lens
643
Q

What is a Barlow Lens?

A

A Barlow lens a piece of kit for astronomers that slots into the eyepiece and increases the magnification by 2x or 3x

644
Q

What is Field Of View (FoV)?

A

The field of view of a telescope is the circle of the sky that is visible through the eyepiece

645
Q

What is a parabolic mirror?

A

A concave mirror that transforms a plane wave into a spherical wave that moves into the centre

646
Q

What are the 4 main sources of light pollution?

A
  1. Commercial and sports floodlights
  2. Urban street lamps and motorway lights
  3. Domestic and industrial security lights
  4. Lights above car parks and shopping centres
647
Q

How long is 1 AU?

A

1 AU = 150 Million km = Distance from the Earth to the Sun

648
Q

How long is one light year?

A

1 l.y. = 9,500,000,000,000 km= 9.5 billion km

649
Q

How long is one Parsec?

A

1 pc = 3.26 l.y. = 3.1 × 10¹³ km

650
Q

What is an H-Alpha Filter?

A

An H-Alpha filter is a filter which is designed to transmit a narrow bandwidth of light. It can be used to observe the features of the Sun

651
Q

Which photoreceptors in a human eye respond to bright lights?

A

Cones

652
Q

What is the approximate diameter of the pupil of the human eye in bright light?

A

3 mm

653
Q

What is Dark Adaption?

A

Dark Adaption is an observing technique where the observer spends time to allow the retina’s rods to desensitise so dimmer stars become more visible

654
Q

What are the components of a reflecting telescope?

A

A reflecting telescope consists of a Concave mirror and Convex lens

655
Q

What is the objective element of a reflecting telescope?

A

Converging mirror

656
Q

Which telescope does an observer not look along its optical axis?

A

Newtonian Reflector

657
Q

Which telescope does an observer not look along its optical axis?

A

Newtonian Reflector

658
Q

Which telescope uses a small diverging secondary mirror to reflect to reflect light back down the ‘tube’?

A

Cassegrain Reflector

659
Q

What is a finderscope?

A

A finderscope is a smaller telescope attached to larger reflectors

660
Q

What is more important: Resolution or Magnification

A

Resolution

661
Q

How is a Keplerian refractor different to a Galilean refractor?

A

A Keplerian refractor consists of two concave lenses whereas, a Galilean refractor has one

662
Q

What is the resolution of a telescope proportional to?

A

Resolution of a telescope proportional to the diameter of the objective element

663
Q

A small inexpensive telescope would be most likely what type of telescope?

A

Keplerian Refractor

664
Q

What are the advantages of having a reflecting telescope over a refractor? (NAME 3)

A
  1. Higher magnifications
  2. Larger objective diameters
  3. Shorter physical lengths
665
Q

What was the space probe Magellan’s target?

A

Venus / Orbiter

666
Q

What was the space probe New Horizon’s target?

A

Pluto & outer Solar System / Fly-by

667
Q

What was the space probe Deep Impact’s target?

A

Comet Tempel 1 / Impactor

668
Q

What was the space probe Juno’s target and what type of probe was it?

A

Jupiter / Orbiter

669
Q

What was the space probe Huygens’ target and what type of probe was it?

A

Titan / Lander

670
Q

Which space probe made detailed studies of asteroids Vesta and Ceres from orbit?

A

Dawn

671
Q

What are the advantages of a unmanned mission compared to a manned mission?

A

Unmanned missions are cheaper, there is no danger faced towards humans and there are no communication time delays as the mission is pre-programmed with mission commands without the need for human interference

672
Q

Which twin space probes studied the outer gas planets, their ring systems and moons?

A

Voyager

673
Q

What was the space probe Philae’s target and what type of probe was it?

A

76P/Churyumov-Gerasimenko / Lander

GCSE Revision Flashcards (24 decks)

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