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Astronomy > Final Exam > Flashcards

Final Exam Flashcards

1
Q

Spiral galaxy

A

Disc shaped like the Milky Way

Old stars in bludgeon, new stars in disc

Low mass ones have fluffy, loose arms and a small bulge

High mass ones have tight arms and a huge bulge

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2
Q

Elliptical

A

Fuzzy ball of stars

Mainly old stars (NOT forming new stars)

Range in masses from tiny to large

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3
Q

Irregular

A

Oddly shaped- can be dwarf irregular or merging

Dwarf irregular: small and low mass, lots of new stars, still forming stars

Merging irregular: stars don’t hit each other, gas clouds hit and make new stars. Settle down into elliptical galaxy

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4
Q

Gravity can…

A

Bend light, focus it like a lens, and magnify more distant objects

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5
Q

Which observation helped us learn that most of the Milky ways mass is dark matter?

A

Stars and gas orbit the galaxy too fast to be bound by the mass of the visible matter

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6
Q

What is the best analogy for how stars orbit the disk of the Milky Way?

A

The disk is like a ring of Saturn, since each particle orbits Saturn independently depending on keplers laws

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7
Q

Which observation helped us learn that the sun isn’t at the center of the Milky Way?

A

We see more globular clusters on the sky in one direction, rather than being evenly spaced

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8
Q

List the parts of the galaxy in the order that they form

A

Nucleus and halo at the same times disk, spiral arms

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9
Q

Dark matter is difficult to observe because

A

It doesn’t absorb or emit any light at all

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10
Q

Most of the mass of a cluster of galaxies is

A

Dark matter

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11
Q

What is a quasar

A

A galaxy with a very active and very bright supermassive black hole

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12
Q

Distance ladder

A

The distance to stars near the sun in the Milky Way are measured with parallax (let us get luminosities)

Won’t work at great distances, rest of Milky Way and other galaxies are measured with standard candles

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13
Q

Hubbles law

A

More distant galaxies are moving away faster, light is redshifted

More distant galaxies have higher redshift

We see a galaxy as younger than it actually is right now

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14
Q

Cosmic web

A

Clusters of galaxies arranged on a large scale in filaments and empty voids

Most of the mass is dark matter

We can’t see it, we infer it

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15
Q

When we’re galaxies making the most stars

A

When the universe was 1-5 billion years old

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16
Q

What does bubbles law relate?

A

Distance and speed at which it is moving away from us

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17
Q

In the first 5 minutes of the universe when fusion was everywhere, what was fusing?

A

Hydrogen into helium (and a little bit of other stuff)

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18
Q

Photons in the CMB came from

A

Plasma glowing because it is hot, when the atoms formed

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19
Q

The atoms in your body heavier than iron were probably made

A

In supernovae when massive stars died

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20
Q

How much of the milky ways total mass is dark matter?

A

90%

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21
Q

Astronomers were able to measure the mass of the Milky Way by watching stars and applying what law?

A

Keplers law

Watch the orbit speed and orbit size to measure the mass that makes it orbit

22
Q

How did we learn where the sun is in the Milky Way?

A

By mapping the location of globular clusters in the sky

23
Q

Over time the slight amounts of heavier elements in the galaxy’s gas increase due to

A

Stars forging heavy elements in their cores and spreading that material into their deaths

24
Q

Most stars form in the spiral arms of the disk because

A

Gas in the disk enters the arms, slows down, and gets compressed

25
Q

Astronomers suspect dark matter is probably made of

A

Particles that don’t interact with the electromagnetic force

26
Q

What is the strongest evidence for the existence of dark matter in the Milky Way?

A

Stars orbit at about the same speed regardless of how far they are from the nucleus of the galaxy, suggesting there is a lot of invisible mass

27
Q

The best analogy for the spiral arms of the Milky Way is

A

A traffic jam, where stars slow down due to the higher gravity of more mass

28
Q

Compared to other spiral galaxies, the Milky Way is

A

About average size

29
Q

Some galaxies shoot huge powerful narrow jets of high speed particles into space which are detectable at radio wavelengths. Astronomers think these jets are launched by

A

The accretion disk of a supermassive black hole at the center of the galaxy

30
Q

What happens when galaxies collide?

A

The gas clouds hit each other, and new stars form from that gas

31
Q

After large galaxies merge, what kind of galaxy is usually the result?

A

Elliptical

32
Q

If you looked at the rate galaxies make stars and compare this rate at different times in the universes history, you would find the most stars being made

A

When the universe was a few billion years old

33
Q

If you see a large ___ galaxy, you can assume it hasn’t experienced any big mergers

A

Spiral

34
Q

The first galaxies had __ metalicity compared to the Milky Way as it is now

A

Much lower

35
Q

Lost the galaxies in order of star formation rate from making the LEAST stars to making he MOST

A

Elliptical, spiral, irregular

36
Q

Difference between stars currently forming in the Milky Way and the stars currently forming in a dwarf irregular galaxy?

A

The Milky Way newborn stars will be higher metalicity than the dwarf irregular stars

37
Q

Observing what helps you learn more about the first galaxies?

A

A redshirt 7 galaxy

The farther away object

38
Q

If you want to observe an overweight white dwarf go supernova, what should you study?

A

A nearby elliptical galaxy

39
Q

How do astronomers know how galaxies change over time?

A

They ran computer simulations and compared them to observations of galaxies at different distances

40
Q

Why did the most massive galaxies form first?

A

Their dark matter halos had more mass, which pulled in more gas faster

41
Q

What ended up “killing” the large elliptical galaxies?

A

They used up all their gas and couldn’t make new stars

42
Q

If you looked at the total energy of matter, dark matter, and dark energy in the universe you’d find that our universe is made of

A

Mostly dark energy

43
Q

Based on observations and models, astronomers are fairly confident the universe is about

A

14 billion years old

44
Q

The expansion of the universe is like

A

Stretching an infinite piece of elastic, where the space between things increased but it’s not expanding into anything else

45
Q

The fate of the universe (recolapse, big chill, big rip) is determined by the balance between

A

Gravity trying to collapse everything and dark energy pushing everything apart

46
Q

If the universe were recollapsing, we should see distances to supernovae and galaxies…

A

Getting smaller

47
Q

The earth is at the center of

A

… nothing

48
Q

What observations do astronomers make to determine the expansion of the universe?

A

The brightness and redshift of distant supernovae

49
Q

If gravity is exactly the same strength as dark energy, then our universe would

A

Eventually stop expanding

50
Q

Astronomers estimate that our universe is

A

Expanding and the rate of expansion is accelerating

51
Q

All of the elements in your body heavier than hydrogen and helium were made

A

By generations of stars living and dying in the Milky Way

52
Q

The amount of hydrogen, helium, lithium, and deuterium in the universe was determined when

A

5 minutes after the Big Bang, during universe wide fusion

Astronomy (5 decks)

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