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Physics 107 > Test 2 Short Answers > Flashcards

Test 2 Short Answers Flashcards

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1
Q

Why can’t we use Infrared Telescopes?

A

Because Earth is too hot.

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2
Q

How do X-Ray Telescopes Work?

A

Scim photons off metal surfaces.

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3
Q

Why Build Larger Telescopes?

A

Larger areas capture more light - 2x radius = 4 x area.

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4
Q

Why Improve the Resolution of Telescopes?

A

Enables us to differentiate between close objects.

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5
Q

What is Interferometry?

A

Connecting telescopes together to make sharper images than a single large telescope.

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6
Q

Why are Telescopes Built High Up?

A

Atmosphere absorbs light - on mountains there is less atmosphere so less distortion.

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7
Q

What is Twinkle?

A

Refracts starlight in random directions very quickly.

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8
Q

What is Wien’s Law?

A

A star’s temperature is related to its colour.

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9
Q

How are Hydrogen Lines Effected by Temperature?

A

Hotter = less hydrogen lines.

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10
Q

What is the Use of Standard Candles?

A

If we know the type of star (and also brightness), we can compare this value with how bright it appears to get a distance.

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11
Q

How do we know the Type of Star?

A

Obtain a spectrum and compare it with other stars with similar spectra whose distances and brightness we know.

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12
Q

What is the Inverse Square Law?

A

Light spreads out with the square of the distance - with a sphere 2x as large, energy covers 4x area.

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13
Q

How does Magnitude Relate to Brightness?

A

Increased magnitude, decreased brightness.

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14
Q

What does m Stand for?

A

m - Apparent magnitude.

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15
Q

What does p Stand for?

A

p - Parallax.

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16
Q

How do we get the Radius?

A

A small hot star can have the same luminosity as a large, cool object.

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17
Q

What are Spectroscopic Binaries?

A

Systems in which stars are so close together that they appear as a single star even in a telescope.

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18
Q

What are Apparent Binaries?

A

Stars seem close together but are not physically connected.

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19
Q

What are Visual Binaries?

A

Stars seem close together and are physically connected.

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20
Q

What are the 3 Things Determined by Mass?

A

Luminosity, radius, temperature.

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21
Q

Why does Increased Mass = Increased Luminosity?

A

More massive stars have greater gravity compression. They need higher core temperatures to be stable and have very many more nuclear reactions.

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22
Q

Why do More Massive Stars Live for Less Time?

A

Because luminosity increases faster than fuel.

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23
Q

Why does High Temperature = Nuclear Fusion?

A

Nuclei can get close enough to fuse.

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24
Q

Why does Low Temperature = No Nuclear Fusion?

A

Electrical repulsion prevents fusion.

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25
Q

What Size are Solar Type Stars?

A

Less than 8 solar masses, greater than 0.8.

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26
Q

What is the S-Process?

A

Adding protons to make things heavier and heavier.

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27
Q

What Size are Low Mass Stars?

A

Less than 0.8 solar masses.

28
Q

What Percentage of Stars are Binaries?

A

75%.

29
Q

Why can’t Binaries Become Red Giants?

A

H envelope will be lost, secondary star may accrete some mass.

30
Q

What is Unique about Degenerate Stars?

A

More mass = smaller size.

31
Q

What are White Dwarfs?

A

What remains of the core of low mass stars that have undergone evolution.

32
Q

Why do Neutron Stars Spin so Fast?

A

Because angular momentum is conserved.

33
Q

Where do New Stars Form?

A

Interstellar gas.

34
Q

Where are Stars Arranged in terms of Age?

A

New stars in the disk, old stars in the halo.

35
Q

What are the 5 Characteristics of Population 1 Stars?

A

Ordered motion, circular orbits in disk, plane, younger, more metal rich.

36
Q

What are the 4 Characteristics of Population 2 Stars?

A

Random motion, eccentric orbits passing through disk plane, older, more metal-poor.

37
Q

What are the 3 Main Types of Galaxy?

A

Spiral, elliptical, irregular.

38
Q

How Old is the Universe?

A

13.8 billion years old.

39
Q

How Old is the Sun?

A

4.6 billion years old.

40
Q

How can we Identify the Shape of the Milky Way?

A

Lots of stars visible in the disk, not many visible in other directions.

41
Q

Which Stars Move Fastest in terms of Proximity?

A

Closer stars appear to move quicker than distant stars.

42
Q

How Big is the Milky Way?

A

100,000 light years in diameter.

43
Q

What is Harlow Shapley Responsible for?

A

Mapping distribution of globular clusters.

44
Q

What are Oort and Lindblad Responsible for?

A

Concluding that the galaxy rotates, structure of the Milky Way.

45
Q

Where are Blue Stars Located?

A

In disks and spiral arms.

46
Q

Where are Red Stars Located?

A

In central bulge and halo.

47
Q

What are Population 1 Stars?

A

1 million to 1 billion years old, high metal concentration.

48
Q

What are Population 2 Stars?

A

10 billion years old, low metal concentration.

49
Q

When was Radio Astronomy Invented?

A

1930.

50
Q

How Often would the Sun Rise and Set Without Earth’s Spin?

A

Once a year.

51
Q

What is the Orion Nebula?

A

Star forming region.

52
Q

What did Harlow Shapley Argue about Nebulae?

A

They are ‘local’.

53
Q

What did Heber Curtis Argue about Nebulae?

A

They are galaxies.

54
Q

How are Telescopes Measured?

A

According to diameter.

55
Q

What are Cepheid Variables?

A

Big pulsating stars - population 1 and population 2.

56
Q

What is One Piece of Evidence of an Expanding Universe?

A

Distant galaxies move faster than nearby ones.

57
Q

What did Einstein Believe about the Universe?

A

It is static.

58
Q

What does Einstein’s Cosmological Principle Assume?

A

The universe is isotropic and homogeneous.

59
Q

What does Isotropic Mean?

A

Same in every direction.

60
Q

What does Homogeneous Mean?

A

Same in every place.

61
Q

How did Einstein Explain the Expanding Universe?

A

Increase in space, nothing moves.

62
Q

How did Newton Explain the Expanding Universe?

A

Space stays the same, but everything moves outwards.

63
Q

How can we Identify the Type of Universe we Live in?

A

Critical density - above means closed (recollapse), below means open (expand forever), equal to means flat (expand forever).

64
Q

What is the Size of the Universe?

A

40 light years across.

65
Q

How does Gravity Work in White Dwarfs?

A

Electrons run out of room to move around, preventing further collapse.

66
Q

How does Gravity Work in Neutron Stars?

A

Neutrons run out of run to move around, preventing further collapse - smaller than white dwarfs.

67
Q

How does Gravity Work in Black Holes?

A

Gravity wins and nothing prevents collapse.

Physics 107 (7 decks)

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