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Astronomy-Zoe Brown > Topic 1:earth,moon and sun > Flashcards

Topic 1:earth,moon and sun Flashcards

1
Q

What are key features of the earth

A
  • it’s atmosphere is mainly oxygen (21%)and nitrogen (78%) it also contains argon(1%) and carbon dioxide (0.04%)
  • liquid water covering about 70% of the surface
  • life in all its diverse forms
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2
Q

What is the diameter of the earth

A

13,000km

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3
Q

What shape is the earth

A

Oblate spheroid

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4
Q

What evidence suggests that the earth is spherical

A
  • ships disappear over the horizon
  • satellites orbit the earth-impossible with a flat earth
  • the curvature of the earths shadow during a partial lunar eclipse
  • images of earth from space
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5
Q

What is latitude

A

The angle between a point on the earth’s surface, the centre of the earth and a point on the equator

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6
Q

How do the lines of longitude run on a globe

A

They converge towards the poles

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7
Q

How much is the Earth’s polar axis tilted by

A

66.5 degrees to the ecliptic

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8
Q

What is the ecliptic

A

The plane on which the Earth orbits the sun

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9
Q

What is the longitude

A

The angular displacement east or west of the observers meridian from the prime meridian

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10
Q

What is the meridian

A

A circle of constant longitude passing through a given place on the earths surface and the terrestrial poles

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11
Q

What is the zenith

A

The point in the sky or celestial sphere directly above an observer

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12
Q

What is an observers horizon

A

The imaginary plane that meets the observer at a tangent to the Earth’s surface

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13
Q

What are the main sources of terrestrial light pollution

A
  • commercial and sports floodlights
  • urban street lamps and motorway lights
  • lights above car parks and shopping centres
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14
Q

What is the height of the atmosphere

A

100km

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15
Q

What benefits does our atmosphere provide is with

A
  • it absorbs harmful solar ultraviolet radiation
  • it absorbs harmful energetic x-rays and gamma-rays from space and prevents them from reaching the ground
  • it provides us with oxygen to breathe
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16
Q

What are the drawbacks of our atmosphere

A
  • the refraction of light as it passes through our turbulent atmosphere, causing stars to ‘twinkle’ and therefore restricts the resolution of an image
  • the selective scattering of shorter wavelengths of sunlight by gas molecules in the atmosphere, making the sky appear blue and so astronomers cannot observe during the day
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17
Q

What effects does the atmosphere have on radiation

A
  • the longest waves are reflected back into space by electrons in the ionosphere
  • some shorter wavelength microwaves are absorbed by water vapour and oxygen
  • ultra-violet radiation is absorbed by ozone and , at shorter wavelengths oxygen
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18
Q

What is a refractor telescope

A

A telescope in which a glass convex lens collects the light and brings it in to a focus

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19
Q

What is a reflector telescope

A

A telescope in which a curved mirror collects light

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20
Q

What is the lens or mirror in a telescope called

A

The objective

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21
Q

What are the advantages of large telescopes

A
  • the collection of more light

* higher resolution in better proportional diameter

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22
Q

What do ideal observing sites consider

A
  • atmospheric properties such as cloud cover, air turbulence, sky brightness, water vapour content
  • geographic location- access, utilities, likelihood of earthquakes and ground stability
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23
Q

What are the benefits of using telescopes in space

A
  • no atmosphere to reduce resolution
  • no light pollution
  • no adverse weather problems
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24
Q

What are drawbacks to using space telescopes

A
  • More expensive to build and launch into orbit
  • reduced lifetime ;
    * difficult/impossible maintenance/repairs/. upgrades
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25
Q

What are the van Allen belts

A

Two doughnut-shaped rings of spiralling high-energy particles held in place by the earth’s magnetic field.

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26
Q

What are the inner van Allen belts made of and how were they formed

A

The compact inner belt consists mainly of high-energy protons formed by collisions between cosmic rays and atoms in the atmosphere

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27
Q

What are the outer van Allen belts made of

A

Consists mainly of electrons and other charged particles emitted by the sun as a result of increased solar activity

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28
Q

What is the diameter of the moon

A

About 3,500km

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29
Q

What is the mean distance that the moon orbits the Earth at

A

380,000 km

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30
Q

What is the moons rotational and orbital period

A

27.3 days

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31
Q

What are rilles on the moon

A

Narrow channel-like depressions in the lunar seas that can either be straight,smoothly-curved or sinuous . They are caused by lava flows

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32
Q

What are wrinkle ridges

A

They are caused by the buckling of the lunar surface as a result of compressive forces within the cooling, contracting lava, forming ridges up to hundreds of kilometres long

33
Q

Name 3 objectives of NASA’s Apollo space programme

A
  • the collection of lunar soil and rock for analysis
  • the deployment of scientific experiments on the lunar surface
  • land a man on the Moon and return him safely to Earth
34
Q

What were some of the instruments in each ALSEP (apollo lunar surface experiment package) employed to measure, analyse and monitor

A
  • the structure of the moons interior
  • lunar dust
  • the intensity and direction of the solar wind
35
Q

What hypothesis is believed to be true for the formation of the Moon

A

The Giant Impact Hypothesis- in which the relatively young Earth was struck by a mars-sized object known as Theia . Theia and a large portion of the earths outer layers melted and merged, and at the same time a huge amount of debris was thrown into the Earth-orbit. This material coalesced and cool d to formed what is now the moon

36
Q

What is the diameter of the sun

A

1.4 million km

37
Q

How far away is the sun from Earth

A

150 million km

38
Q

What is the temperature of the photosphere

A

5800 k

39
Q

What is the ‘visible’ surface of the sun

A

Photosphere

40
Q

What gasses make up the sun

A

75% hydrogen and 25% helium

41
Q

What makes up the suns atmosphere

A

The chromosphere and the corona

42
Q

How thick is the suns atmosphere

A

2,000km

43
Q

What is the temperature of the corona

A

2 million k

44
Q

Why does the sun shine

A

Because it is able to turn gravity into light- happens because hydrogen gas in the core gets squeezed together so tightly that 4 hydrogen nuclei combine to form one helium atom, this is called thermonuclear fusion

45
Q

What is the safest way to view the sun

A

Use and indirect projection method in which a pinhole camera, pair of binoculars or a telescope focuses an enlarged image of the sun onto a screen, reducing the brightness to a safe level

46
Q

What are sunspots

A

Small dark patches on the photosphere and they are cooler areas of the photosphere

47
Q

What is an umbra

A

A central darker region, about 2,000 k cooler than the photosphere

48
Q

What is a penumbra

A

A lighter surrounding area, with a temperature about 200 k cooler than the photosphere

49
Q

What is the suns rotational period

A

25 days at the equator and 36 days at its poles

50
Q

What is solar wind

A

A steady stream of charged particles (mainly protons and electrons, but with traces of ions of helium and other elements)

51
Q

Where is solar wind found

A

Flowing outwards in all directions from the suns corona at speeds of typically 400km/s

52
Q

What are coronal holes

A

Cooler region of the corona close to the suns magnetic poles

53
Q

What happens when a telescope is fitted with a H-alpha filter

A

The filter allows a narrow range of wavelengths either side of 656nm to pass through and block the remaining light. The increased contrast allows solar features to be observed clearly

54
Q

What are prominences

A

Huge clouds of cooler gas in the sun’s atmosphere

55
Q

What are filaments

A

Huge clouds of cooler gas in the sun’s atmosphere that appear as dark silhouettes against the brighter photosphere

56
Q

What are solar flares

A

Sudden releases of energy

57
Q

What happens when an x-ray filter is used

A

Exceptionally hot regions of the sun emit x-rays and so an x-ray filter allows you to see them

58
Q

How long is the lunar cycle

A

29.5 days

59
Q

Why is the moon visible

A

Because it reflects sunlight

60
Q

What is a solar eclipse

A

When the moon is on the ecliptic and it moves directly in front of it and so blocking it out

61
Q

What phase does the moon have to be in for a solar eclipse to happen

A

New moon

62
Q

Why don’t solar eclipses happen every new moon

A

Because the plane of the moon’s orbit around the earth is tilted slightly to the plane of the earth’s orbit around the sun.this means that at most new moon’s the moon is either ‘above’ or ‘below’ the sun in the sky

63
Q

What is a lunar eclipse

A

When the moon is on the ecliptic and it moves directly behind the earth so that the light from the sun is blocked out

64
Q

What phase doe the moon have to be for a lunar eclipse to happen

A

Full moon

65
Q

Why does the moon go red/orange in a lunar eclipse

A

The light from the sun passes through the atmosphere around the edge of the the Earth and most blue light is scattered to leave mainly red light.this red light is refracted by the Earth’s atmosphere and illuminates the moon

66
Q

How long is a sidereal day

A

23 hrs 56 min

67
Q

How long is a solar day

A

24hrs

68
Q

Why doesn’t the sun move over the sky in a uniform matter every day

A
  • the earth orbits the sun in an elliptical orbit
  • the earth’s polar axis is tilted to the plane of its orbit,causing the sun to b ‘higher’ no the sky in summer compared to winter
69
Q

What is the equation of time

A

EOT=apparent solar time-mean solar time (GMT)

70
Q

What are Aurorae caused by

A

Electrons from solar wind, that have been accelerated to high speeds in the Earth’s magnetic field , exciting atoms and molecules of oxygen and nitrogen in the upper atmosphere. As the atoms de-excite, they emit light at certain wavelengths that are characteristic of the element concerned

71
Q

What is the Tropic of Cancer

A

The circle marking the latitude 23.5o north- where the sun is directly overhead at noon on June 21

72
Q

What is the Tropic of Capricorn

A

The circle marking 23.5o south- where the sun is directly overhead on December 21

73
Q

How is the far side different to the near side of the moon

A

Less Maria and more crators

74
Q

What month do shadow sticks give the shortest shadows at noon in the U.K.

A

June

75
Q

What does a sunrise determine

A

The apparent solar time

76
Q

What was the name of the first successful manned exploration of the moon

A

Apollo 11 in 1969

77
Q

What did Eratosthenes observe

A

He read an account that at noon on the date of the summer solstice in Syene on the Tropic of Cancer, the sun lay directly over a well. Furthermore, vertical sticks and columns of temples did not cast any shadows at that precise time in Syene

78
Q

What was Eratosthenes method

A

Measurements of the suns position at noon in alexandria on the summer solstice showed that it was just over 7° from the zenith which is equivalent to almost exactly 1/50th of a circle

He learnt that Syene was the
equivalent of 790 km further south the Alexandria and so he used geometry to deduce that the circumference of the earth was 50 times this value i.e. 39,500km

79
Q

When if the summer solstice

A

21st June

Astronomy-Zoe Brown (9 decks)

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