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Astronomy GCSE Edexcel > Topic Three: Stars > Flashcards

Topic Three: Stars Flashcards

1
Q

How many stars can you see with the naked eye?

A

2,000 if:

-moonless night, no light pollution

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2
Q

What is a constellation?

A

An area in the night sky containing a particular pattern of stars

88 total

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3
Q

What are asterisms?

A

Groups of stars that form familiar shapes

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4
Q

Give an example of an asterism:

A

The plough

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5
Q

Describe the constellation Orion:

A

Asterism of Orion’s belt
-Pointer stars to Aldevaran (up and to the right)
-and Sirius (down and to the left)
Contains the Orion Nebula

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6
Q

Describe the Winter Triangle:

A

Sirius, Procyon, Betelgeuse

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7
Q

Describe the Bayer Designation Naming Scheme:

A

Brightest star in constellation is Alpha
Then Beta, Gamma, Delta, Epsilon… as stars get dimmer
1st 3 letters of the constellation of which the star is found.

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8
Q

Use the BDNS to name the 2nd brightest star in constellation Centaurus:

A

β cent

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9
Q

How would you find Andromeda in the night sky?

A

From the top left corner of the square of Pegasus, jump two stars left and two up

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10
Q

What is Fomalhaut?

A

The star of which the first exoplanet was discovered

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11
Q

What is Declination?

A

If we imagine Earth at the centre of a giant celestial square, declination is almost identical to Latitude

It is the angle of a point above the celestial equator

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12
Q

What is right ascension?

A

The angle between the star and the celestial prime meridian.

Measured in hours and minutes

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13
Q

What is the Celestial Prime Meridian?

A

The point on the celestial equator on which the sun moves from the southern to northern equator

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14
Q

What is the zodiacal band?

A

The part of the sky that contains the constellations of the Zodiac

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15
Q

Why do stars appear to rotate about Polaris?

A

Anticlockwise

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16
Q

How can we determine if a star will be circumpolar using the observer’s latitude and the stars declination?

A

Declination > 90 - latitude

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17
Q

What is a circumpolar star?

A

A star that is always above the observer’s horizon

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18
Q

Explain how a star will be circumpolar from a given latitude so long as the declination is > 90 - latitude:

A

For example:

My latitude is 52 degrees

  • 90-52 = 38 degrees
  • Therefore any state with a declination>38 degrees will be circumpolar
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19
Q

Name 4 considerations when planning an observation:

A

Phase of the moon

Equipment

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20
Q

What else is ideal for observing stars?

A

Dark adapted vision
Relaxed eye
Averted vision

21
Q

Explain the difference between Optical Double stars and True Binary stars:

A

True Binary stars are linked together Gravitationally and orbit a common centre of mass

Optical Double stars merely appear nearby but may be light years apart

22
Q

Give an example of a Binary star:

A

Castor in Gemini

23
Q

How many times brighter is a star with a magnitude of 5 compared with a star with a magnitude of 1?

A

100 times

24
Q

Give 4 factors that affect the apparent magnitude of a star:

A 
Energy radiated by star:
- Size 
- Temperature 
Interstellar gas and dust 
Amount of light absorbed by Earth's atmosphere 
Distance from Earth
25
Q

What is the magnitude of the brightest star in the sky?

A

1.5 Sirius

26
Q

What is the Absolute Magnitude?

A

A measure of Apparent magnitude if observed from a distance of 10pc

27
Q

Name two types of variable star:

A

Cepheid Variables

True Binaries

28
Q

What is a Cepheid Variable?

A

A giant yellow star that regularly expands and contracts in size

29
Q

What is an eclipsing Binary?

A

If two binary stars orbit each other in a plane along our line of sight, two stars will eclipse each other

30
Q

What is the Primary Star in a Binary Star?

A

The brighter star

31
Q

What is a Parallax?

A

The apparent motion of near and more distant objects in respect to each other, caused by the motion of the observer

32
Q

What is the definition of a parsec?

A

The distance at which a star would have a parallax angle of one arc-second

33
Q

How are Cepheid Variables used to determine stellar distances?

A

Using the period - luminosity law we can work out the absolute magnitude of the star
Use the distance modulus formula to calculate distance
m - M = -5 + 5logd

34
Q

What are stars formed from?

A

From huge clouds of gas and dust called nebulae

35
Q

Where are nebulae usually found in a Galaxy?

A

In the spiral arms

36
Q

How are stars formed?

A

Nebulae begin to collapse and break up into protostars.
There is a rise in temperature and pressure as GPE and KE.
When the temperature reaches 15 million K in the core, fusion starts

37
Q

Describe a star’s death (up to red giant):

A

Star runs out of hydrogen
No radiation countering gravitational collapse
Star collapses
Temperature rises further
Fusion restarts in a shell surrounding the core, meaning the outer layers of the star expand and cool to form a red giant

38
Q

Describe a main sequence star’s death (from red giant):

A

Helium nuclei fuse to form Carbon
When helium is depleted, the red giant loses its outer layers in an expanding shell of gas forming a planetary nebula
Core collapses to form White dwarf, cools eventually to brown and then black

39
Q

Describe a larger star’s death (from red giant):

A

Super red giants can form iron through fusion, this makes a Supernova.
The star will then become a neutron star, of a Black Hole if it’s big enough

40
Q

What is a supernova?

A

A massive explosion at the end of a supergiant star’s life

Outer layer blown away at speeds of 5000km/s

41
Q

What is a neutron star?

A

A remnant of a supernova
Mass of sun collapsed into a sphere of 20 km diameter
Intense gravitational fields cause them to spin
Emit radio waves from their polar regions

42
Q

How can we deduce the chemical composition of a star?

A

Each element has its own unique set of spectral line wavelengths
Analysis of starlight can tell us what the star is made of

43
Q

How can we deduce the temperature of a star?

A

The temperature of a star determines its colour, so spectral analysis can determine its temperature

44
Q

How can we determine the radial velocity of a star?

A

Analysis of the Doppler shift of spectral lines

45
Q

What is a HR diagram?

A

This is a plot of luminosity against spectral type

46
Q

Which stars will run out of fuel sooner?

A

Massive stars

47
Q

Give evidence for the existence of Neutron stars:

A

Regular pulsating radio signals from Pulsars

48
Q

Give 3 pieces of evidence for the existence of black holes:

A

Light bent by black hole’s gravity

Speed of rotation of our galaxy and its size hints that the mass at its centre is great enough to be a black hole

Charged particles spinning around a Black hole produce x rays which we can detect

Astronomy GCSE Edexcel (6 decks)

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