Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Astronomy And Space Science > Star Remnants, Milky Way, Cosmology > Flashcards

Star Remnants, Milky Way, Cosmology Flashcards

1
Q

What is a neutron star? How are they formed?

A

A neutron star is an incredibly dense sphere composed primarily of neutrons. During the core collapse of massive stars protons and electrons combine to form neutrons.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the maximum mass of a neutron star?

A

2-3 M

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are pulsars?

A

Fast spinning neutron stars.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Give two reasons why pulsars cannot be white dwarfs.

A

White dwarfs would be torn apart by such fast rotation.
Pulsars could be found in supernova explosion where no white dwarf can remain.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

T or F. All neutron stars are pulsars.

A

False.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are X-ray bursters?

A

Equivalent to novae for neutron stars.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are black holes?

A

Black holes are the remains of explosions from very massive stars where neither light or matter can escape its gravitational force. This happens when the remaining core is too big to form a neutron star.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

T or F. A 5M black hole comes from a 5M star.

A

False. A much bigger star would be needed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Why does no light escape from a black hole?

A

The escape velocity exceeds the speed of light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the schwarzschild radius?

A

Is the radius of a sphere around black hole from within no light can escape.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is event hoizon?

A

A space-time boundary around a black hole from within which nothing can escape.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is singularity?

A

The centers of a black hole, where density, gravity and the curvature of space-time are infinite.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

T or F. When a star becomes a black hole, its gravitational pull becomes stronger.

A

False.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

T or F. The larger a black hole the weaker the gravity near its Schwarzschild radius.

A

True.

The singularity itself is further away the bigger the black hole.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is gravitational lensing?

A

Light coming from behind the black hole will curve around the black hole, distorting our view of objects behind the black hole.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is gravitational redshift?

A

From an observer point of view, matter falling into a black hole gets redder as it gets closer to the event horizon.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is gravitational time dilation?

A

From an observer point of view, as an object gets closer to the event horizon of a black hole, time seems to slow down. So much that it will take an infinite amount of time to fall inside the black hole.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the two types of gamma ray burst?

A

Long duration: Collapse of very massive stars. Type 1c supernovae.

Short duration: Merging of neutron stars or black holes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

T or F. Gamma ray bursts are the most powerful events in the universe.

A

True.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

T or F. Gamma ray bursts are the most distant sources in the Universe that we have detected.

A

True.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

T or F. All GBR have detectable optical afterglows.

A

False.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What are gravitational waves?

A

They cause the space-time continuum to stretch and squeeze.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How far away from the galactic center of the milky way is the sun?

A

8 kpc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the diameter of the milky way?

A

50 kpc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is the distribution of young vs old stars in the milky way?

A

More young stars are in the spiral arms, old stars are evenly distributed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How can we map the arms of the milky way?

A

Using radio observations we study how stars move around the galaxy. Because they are moving they will show Doppler shifts, so we can tell whether they are moving toward or away from us.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How many major arms does the Milky Way have?

A

4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the evidence for dark matter?

A

The orbital speed of stars and gas around the galactic center is nearly uniform throughout most of our Galaxy. If the Sun and stars obeyed Kepler’s third law, the orbital speed would be less for stars in larger orbits. As this does not happen there must be a large amount of mass in the galaxy that cannot be detected.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

How much of the milky way is theorized to be dark matter?

A

Almost 90%
Extends 2-4 times the size of the halo.

30
Q

We expect the rotation curve of our Galaxy to decrease rapidly after the approx visible edge, what actually happens?

A

It increases.

31
Q

T or F. The black hole at the center of our galaxy is currently in a quiet state.

A

True.

32
Q

What is the name for a galaxy with an active supermassive blackhole?

A

Active Galactic Nuclei (AGN’s)

33
Q

Why is it important the Solar System is a large distance from the center of the galaxy?

A

Gamma ray emissions from the supermassive black hole at the centre of the Milky Way have likely led to very high radiation levels near the centre of the galaxy.

34
Q

T or F. Spiral galaxies evolve into elliptical galaxies.

A

False.

35
Q

Define spiral galaxies.

A

Spiral arms + large central bulges
High star formation rates.

36
Q

Distinguish between Sa, Sb, Sc.

A

Sa = 4% gas and dust = more tightly wrapped arms
Sb = 8%
Sc = 25% = less tightly wrapped arms

37
Q

Define barred spirals.

A

Spiral Arms
Size of the bar is greater than the bulge.
High Star formation rates.

38
Q

What type of galaxy is the milky way?

A

Barred spiral.

39
Q

Define elliptical galaxies.

A

Lack of star formation - little dust
No spiral arms
Majority old stars

40
Q

Distinguish between E0, E3 and E6.

A

Only difference is perception from Earth.

41
Q

Define lenticulars.

A

Have bulges and disks like spiral galaxies.
They do not have spiral arms.

42
Q

For each type of galaxy state its primary star type in terms of population.

A
  • Spirals: Spiral Arms: Population 1
    Nucleus and Disk: Population 2 and Old Population 1
  • Elliptical: Population 2 and Old Population 1
  • Irregular: Population 1
43
Q

What is produced by gravitational lensing when a distant blue galaxy is almost entirely behind the gravitational lens?

A

An Einstein ring

44
Q

What can gravitational lensing tell us about dark matter?

A

We can measure the total mass of the overall object that has created the effect, dark matter is needed to account for this total mass.

45
Q

Give redshift formula.

A

z = (lambda observed - lambda) / lambda

46
Q

State Hubble’s law.

A

The more distant a galaxy the greater its redshift and the more rapidly it is receding from us.

H0 = velocity / distance
Age of the universe = 1 / H0

47
Q

Give approx H0 and hence age of universe.

A

H0 = 73 km/s/Mpc
13.7 billion years old

48
Q

T or F. As the universe expands galaxies move away from each other through empty space.

A

False.

49
Q

T or F. As space expands it carries galaxies along with it.

A

True.

50
Q

T or F. Light from stars is doppler shifted by their movement, but the wavelength then remains constant as it travels to Earth.

A

False.

51
Q

T or F. As the universe is expanding, galaxies that were in a cluster are more spread out then they were billions of years ago.

A

False.

Gravitational attraction binds the cluster together locally as the universe expands.

52
Q

What is the Cosmic Microwave Background Radiation?

A

Isotropic emission in all directions believed to be an echo of the Big Bang. Origin of the universe.

53
Q

To what temperature has the universe cooled.

A

2.725K

54
Q

What does a dark area/bright area mean on CMB?

A

Dark areas: cooler regions where the early Universe was more dense than average.

Bright areas: warmer regions where the early Universe was less dense than average.

55
Q

What is the problem with the hubble constant?

A

The constant obtained by CMB does not match than of SN type 1a.

56
Q

What is sigma 0?

A

Is a density parameter that describes the combined average mass density of the universe, p0, in terms of a critical density, pc.

sigma 0 = p0 / pc

57
Q

What happens if
(a) sigma 0 (density) > 1 (critical density)
(b) sigma 0 (density) = 1 (critical density)
(c) sigma 0 (density) < 1 (critical density)

A

(a) spherical shape, parallel light beams converge
(b) flat shape, parallel light beams remain parallel
(c) hyperbolic shape, parallel light beams diverge.

58
Q

What is sigma 0 from observation?

A

= 1
Consistent with a flat universe.

59
Q

Explain why we need dark energy.

A

CMB points to sigma 0 = 1
But if matter and radiation are all there is sigma 0 = 0.24

Solution is some form of energy we cannot detect, which accounts for the missing 76% of the total energy of the universe.

60
Q

How much of the universe is dark energy in theory?

A

76%

61
Q

T or F. The rate of expansion of the universe is slowing down.

A

False.

Is speeding up!

62
Q

How much of all matter is dark matter?

A

85-90%

63
Q

Explain the stages of the big bang.

A

During the inflationary epoch, the plasma of photons and charged particles expanded by an immense factor.
Recombination period saw the first atoms, CMB emitted after 380,000 years.
At 400 million years, first stars and later galaxies.

64
Q

Which of the following is NOT a property of a pulsar?

Question 5 options:

period of 1.34 seconds

each pulse consisting of a 0.01 second burst of radiation

over time, the period is gradually increasing

time interval between pulses is very uniform

emissions only in the visible part of the spectrum

A

Emissions only in the visible part of the spectrum

65
Q

In binary neutron star systems, the orbits are expected to slowly decay, eventually resulting in a merger of the neutron stars. Where does the orbital energy go?

Question 13 options:

It is emitted as neutrinos.

It is emitted as gravitational waves.

It is emitted as gamma-rays.

It is converted to mass.

It is lost to friction.

A

It is emitted as gravitational waves.

66
Q

T or F. Closed universe = sphere

A

True.

67
Q

Formula for radius of a black hole.

A

2GM / c^2

68
Q

What is the mass of sun? What is G?

A

2 * 10^30kg

6.67 * 10^-11

69
Q

Observed temperature fluctuations in the Cosmic Microwave Background Radiation are of what degree?

A

tens of millionths of a kelvin

70
Q

What use are 21 cm radio waves to galactic astronomers?

Question 47 options:

They bounce off stars like our Sun to let us precisely measure their distances.

They pick up the cool, dark matter much better than can optical telescopes.

They cut through the dusty cocoons to let us watch star birth.

We can reflect them off the core of the Galaxy.

Their Doppler shifts let us map the motions and locations of gas in the spiral arms.

A

Their Doppler shifts let us map the motions and locations of gas in the spiral arms.

71
Q

An object slightly more massive than the Sun, but roughly the size of a city, is a?

A

Neutron star

72
Q

AU to metres

A

1 AU ≈ 1.496 × 10^11 meters.

Astronomy And Space Science (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions