phys final 2

true/false and participation

Gas is added to the interstellar medium by supernovae and planetary nebulae. What kind of gas would you expect that to be?

mostly hydrogen and helium, with a mix of heavier elements in it, such as carbon, oxygen, silicon, iron, and so on

Why is it difficult to get a good picture of what the Milky Way Galaxy looks like?

All of these options

About how long does light take to reach us from the nearest star besides the Sun? (The Sun takes 8

minutes.)

about four years

About how long does light take to cross the disk diameter of the Milky Way Galaxy?

about 100,000 years

What does our galaxy look like?

It has a large disk with spiral arms, and it is relatively flat and thin

Which of the following statements best explains what halo stars tell us about the Milky Way’s history?

Halo stars are old and contain fewer heavy elements than disk stars, indicating they formed early.

What key evidence challenges the "simple model" of galaxy formation?

The presence of stellar streams and disrupted dwarf galaxies in the halo

Which statement is true about elliptical galaxies?

They consist mostly of older stars and are common in large galaxy clusters

Why do spiral and irregular galaxies appear blue-white in color?

Ongoing star formation produces short-lived, bright blue stars

Which method in the distance ladder relies on bouncing radar signals off of nearby planets?

Radar ranging

Why are white-dwarf supernovae useful as standard candles?

They all have the same luminosity because they explode at the same mass.

What was the main issue debated during the Great Debate of 1920?

Whether spiral nebulae were galaxies outside the Milky Way

How did Edwin Hubble settle the Great Debate?

By using Cepheid variables to determine Andromeda's distance

What does Hubble's Law state?

Velocity = H₀ × distance

Why do more distant galaxies appear to be moving away from us faster?

There is more expanding space between us and distant galaxies, so the total velocity is greater

What is the Cosmological Principle?

Matter is evenly distributed on large scales, with no center or edge

What is the primary evidence that quasars are extremely distant?

Their highly redshifted spectra

The center of galaxy M87 has been shown to host a black hole with a mass of approximately

2–6 billion solar masses

What key process converts gravitational potential energy into thermal radiation near a black hole?

Friction in an accretion disk

What relationship has been observed between galaxies and their central black holes?

Black hole mass correlates with the galaxy's bulge mass

Which of the following is NOT a characteristic of a radio galaxy?

Jets that primarily emit visible light

The evidence for a supermassive black hole at the center of the Milky Way includes:

Both B and C

If the region we observe in infrared light near the center of the Milky Way is about 200 light-years across initially, how much smaller is the supermassive black hole (Sagittarius A*) compared to this initial view?

8 orders of magnitude smaller

What does the CMB’s nearly uniform temperature tell us about the early universe?

The early universe was very hot and nearly smooth

How did inflation help explain where structure in the universe came from?

It made tiny ripples bigger, which is where structure eventually grew

What does inflation explain about the shape (geometry) of the universe?

Inflation flattened the universe’s shape

Why is the cosmic microwave background now in the form of microwaves?

The universe stretched the light to longer wavelengths

What do patterns in the CMB support about the early universe?

Inflation probably happened

Why does the night sky being dark support the Big Bang theory?

We can see back to a time before stars existed

According to CMB data, what makes up most of the universe’s energy?

Dark energy

What is the rotation curve of a spiral galaxy?

a plot of rotation speed vs. distance from the center

When astronomer Vera Rubin began to measure the rotation curves of spiral galaxies in the 1960s,
she found that

outer regions of the galaxies were rotating faster than expected based on the visible mass of the galaxy

Observations indicate that spiral galaxies rotate much faster than would be expected based on their
visible gas and stars alone. This has led astronomers to conclude that

there must be a lot of dark matter whose gravity can be felt but which cannot be seen

A rotation curve of the moons orbiting Jupiter would look most similar to

a rotation curve for the planets within the solar system

True or False: The rotation curve of our Solar System is similar to the rotation curve of our Galaxy

False

True of False: In our Solar System, planets close to the Sun move quickly as they orbit around the
Sun, and planets far away from the Sun move more slowly. This tells us most of the mass in our Solar
System is concentrated in the center of the Solar System (in the Sun)

True

What do the fast speeds of stars in elliptical galaxies tell us?

There must be a lot of dark matter whose gravity can be felt but which cannot be seen

What would happen to the galaxies within a cluster of galaxies if the dark matter was instantly
removed from the cluster?

The galaxies within the cluster would have escape velocity from the cluster