Astr Final

What lurks at the center of the MGW?

a monster black hole

Evidence for the Big Bang

(i) Cosmic Microwave Background Radiation. (ii) Element abundances in the Universe.

Which formed first? How can you get both?

-bulge, while the big gas cloud was still collapsing -after bulge is created, it accretes more stuff and settles into the disk

How many stars does MWG produce per year? now____ peak formation_____

1 15

Galaxies grow in several ways:

1) keep accreting material from surroundings - gas falls in 2) form stars - convert gas into stars 3) two collide and merge into a bigger galaxy

The MWG disk's thickness is ___/_____ of the disk's diameter.

1/100

How many light years long is the MWG? How many ly are is the sun from the center?

100,000 ly 28,000 ly

We can't see further than _______ light years away, because that's how long the Universe has been around. So ____ billion light years is the __________. It's a horizon in both time and space.

14 billion cosmological horizon

At what angle is the solar system moving from the galaxy's disk?

25 degrees crosses plane every 33 million years

______ of stars in halo are isolated halo field stars.

99%

a possible definition of a galaxy

A galaxy is gravitationally bound system consisting of a stars, stellar remnants, interstellar medium (some galaxies have this some don't) and dark matter.

If our Universe is expanding, what are the implications for the separation between two stars within our galaxy? A. The distance between the two stars is unaffected. B. The two stars are moving farther apart. C. The two stars are moving closer together.

A. The distance between the two stars is unaffected.

When we look at the cosmic microwave background radiation we are looking further into space - ie, farther back in time - than when we look at galaxies. A. True B. False

A. True

Suppose you tried to determine where we are in our home galaxy by counting individual stars in different directions. You would estimate that we are A. at the center of the Galaxy. B. in an arm of the Galaxy. C. near the edge of the Galaxy.

A. at the center of the Galaxy.

Which types of galaxies are likely to contain many M-type stars but very few (if any) O-type stars? A. ellipticals B. spirals C. irregulars D. bothB&C E. none of the above

A. ellipticals

Some of the 'snow' (white noise) you seen on an antenna TV that is not tuned to a station is left over radiation from the early Universe: A. yes B. no C. What is an antenna TV??

A. yes

Inflation has a fundamental problem in that it requires the Universe to increase faster than the speed of light! Relativity says that this is impossible. A. True. B. False, because space itself is expanding faster than the speed of light, but matter isn't moving through space at faster than the speed of light.

B. False, because space itself is expanding faster than the speed of light, but matter isn't moving through space at faster than the speed of light.

Why do astronomers think that star formation is associated with the spiral arm pattern in disk galaxies? A. The arms are the only location where gas exists. B. The arms are waves that help gas clouds collapse. C. The arms are a physically-linked chain of supernova explosions that cause gas clouds to collapse. D. The arms are a wall of dust that smashes into gas clouds and causes them to collapse.

B. The arms are waves that help gas clouds collapse.

Which statement best describes what astronomers mean when they say that the Universe is expanding? A. distance between stars in the Milky Way is increasing with time B. distance between galaxies is increasing with time C. all objects in the Universe, including planets and everything on them, is gradually growing in size D. our known Universe (finding more distant objects), rather than the actual Universe, is growing with time

B. distance between galaxies is increasing with time

Where are the globular clusters (very dense clusters of old stars) located in the Milky Way Galaxy? A. in the disk B. in the halo C. in the bulge D. in the spiral arms

B. in the halo

If the Universe is expanding, what can you conclude about the Universe at earlier times? A. it was less dense and hotter B. it was more dense and hotter C. it was less dense and cooler D. it was more dense and cooler

B. it was more dense and hotter conservation of energy!

What makes up the 'milky' band of light of our galaxy? A. distant glowing white interstellar clouds B. many distant stars too far to resolve with our eyes C. the asteroid belt D. white dust particles in our solar system

B. many distant stars too far to resolve with our eyes

Where are stars forming in our galaxy? A. mostly in halo globular clusters B. mostly in the disk near the spiral arms C. mostly in the disk far from any spiral arms D. mostly in the galaxy bulge E. only at the galactic center

B. mostly in the disk near the spiral arms

In the baking raisin cake analogy, what is expanding in size? A. the cake and each raisin B. only the cake C. only the raisins

B. only the cake

A baking raisin cake is expanding like the Universe, with raisins acting as galaxies. After one hour, raisins #2 and #3 are moving how fast away from raisin #1? A. 3 cm/hour, 3 cm/hour B. 4 cm/hour, 2 cm/hour C. 2 cm/hour, 4 cm/hour D. 2 cm/hour, 2 cm/hour E. 3 cm/hour,6 cm/hour

C. 2 cm/hour, 4 cm/hour

How long would it take the Hubble Space Telescope to observe the whole sky with the same sensitivity as the Hubble Ultra Deep Field? A. About a year B. About a thousand years C. About a million years

C. About a million years

What are the largest structures in the Universe? A. Galaxies B. Galaxy clusters C. Galaxy superclusters, voids, and filaments D. We haven't seen the largest structures yet - they extend past the extent of current surveys.

C. Galaxy superclusters, voids, and filaments

Gas is added to the interstellar medium by supernovae and planetary nebulae. What kind of gas would you expect that to be? A. Hydrogen gas B. Hydrogen + helium gas C. Gas with a mix of heavier elements in it (carbon, oxygen, iron, etc.)

C. Gas with a mix of heavier elements in it (carbon, oxygen, iron, etc.)

Where will the gas in our galaxy be in one trillion years? A. Blown out of the galaxy. B. Recycling like it is now. C. Locked up in white dwarfs and low mass stars.

C. Locked up in white dwarfs and low mass stars.

Can the spectrum of the cosmic microwave background be explained by being due to the combined light of many stars and galaxies? A. Yes, the redshifted light from the very first stars and galaxies can explain the observations of the cosmic microwave background. B. Yes, but astronomers prefer the explanation that the cosmic microwave background resulted from the Big Bang. C. No, stars and galaxies have different temperatures and would not produce a perfect thermal spectrum at a single temperature as observed. D. No, stars produce mainly optical, not microwave radiation.

C. No, stars and galaxies have different temperatures and would not produce a perfect thermal spectrum at a single temperature as observed.

Which stars likely formed first in the universe? A. Stars with more heavy elements than the Sun. B. Stars with a similar amount of heavy elements as the Sun. C. Stars with less heavy elements than the Sun.

C. Stars with less heavy elements than the Sun.

When we look at the farther galaxies in the Hubble Deep Field, we see light radiating from galaxies when they were: A. about 12 to 13 billion years old. B. about 5 billion years old. C. about 1 to 2 billion years old. D. we can't measure their ages.

C. about 1 to 2 billion years old.

What types of stars are found in the Milky Way halo? A. only white dwarfs B. only Sun-like G-type main sequence stars C. many K-type red giants & main-sequence M stars D. all main-sequence types from O to K stars

C. many K-type red giants & main-sequence M stars

Hubble's Law states that A. larger galaxies have greater speeds. B. faster galaxies are more massive. Hubble's Law states that C. more distant galaxies move away from us faster. D. galaxies that rotate faster are more distant.

C. more distant galaxies move away from us faster.

why are ellipticals different from spirals?

Clouds that were denser initially might finish forming all of their stars before gas settles into disk. More spin (angular momentum) in collapsing cloud could lead to spirals, while less spin could lead to ellipticals

Dark Energy

Counteracts gravity - a repulsive force.

How can we measure the rotation speed of a galaxy out past the stellar disk? A. Use supernovae in the halo. B. Use hydrogen clouds out past the stars in the disk. C. Use globular clusters in the halo. D. B+C E. We can't.

D. B+C

According to modern ideas and observations, what can be said about the center of our expanding Universe? A. Earth is at the center. B. The Sun is at the center. C. The Milky Way Galaxy is at the center. D. The Universe does not have a center.

D. The Universe does not have a center.

Why should we be not surprised that galaxy collisions were more common in the past? A. Galaxy velocities were higher in the past. B. Galaxies were larger in the past. C. BothA&Baretrue. D. The universe was much denser in the past, so galaxies were closer together.

D. The universe was much denser in the past, so galaxies were closer together.

In the early Universe: A. the temperature was billions of degrees K. B. the density was enormously high. C. matter could turn into energy and vice versa. D. all of the above E. A+B only

D. all of the above

What is the evidence that star formation occurs near the spiral arms? A. blue stars B. dark clouds of gas and dust C. clouds of ionized gas D. all of the above E. many K-type red giants

D. all of the above

Which types of galaxies appear to have many young stars? A. ellipticals B. spirals C. irregulars D. both B&C E. none of the above

D. both B&C

Which types of galaxies show evidence for significant amounts of dust (and gas)? A. ellipticals B. spirals C. irregulars D. bothB&C E. none of the above

D. bothB&C

What are galaxies made of? 90% _________ 10%___________

Dark Matter Stars, Gas, Dust

Imagine that you could travel at the speed of light. Starting from the Earth, how long would it take you to travel to the center of the Milky Way Galaxy? A. 2 years B. 20 years C. 250 years D. 2500 years E. 25,000 years

E. 25,000 years

Why do astronomers think that major mergers are a good explanation for the formation of ellipticals? A. We observe interacting galaxies. B. Galaxy merging occurs naturally in our cosmological model simulations. C. Computer models of merging galaxies produce properties of mergers & elliptical galaxies. D. We observe more distorted galaxies in the past. E. All of the above.

E. All of the above.

Why should we be not surprised that ellipticals are seen in clusters? A. Clusters have more mass and ellipticals are more massive galaxies than spirals. B. There are more galaxy mergers in clusters. C. There is hot gas in clusters that can strip the disks off of spiral galaxies. D. A+B E. B+C

E. B+C

What are the key ways that the galaxy population has changed over the last 10 billion years? A. Fewer ellipticals now than in the past. B. More ellipticals now than in the past. C. Spirals & elliptical galaxies were smaller in the past. D. Both A&C are true. E. Both B&C are true.

E. Both B&C are true.

The cosmic microwave background has been mapped on the plane of the sky in detail. What does it look like? A. It is seen only in certain directions. B. It is seen in all directions. C. It is seen even where space is 'empty'. D. If you look closely, there are small variations from place to place. E. all of the above except A

E. all of the above except A

What are the dark breaks in the 'milky' band of light of our galaxy? A. dusty clouds of gas that block visible light B. empty breaks in the distribution of distant stars C. rips in the fabric of space-time D. interstellar material from which stars form E. both A & D

E. both A & D

Which types of galaxies likely have only hot O-type stars? A. ellipticals B. spirals C. irregulars D. all of the above E. none of the above

E. none of the above

little to no disk component. No spiral arms

Elliptical Galaxies

What are the three main types of galaxies?

Elliptical, Spiral, Irregular

_________ tend to be found in huge clusters of galaxies (up to hundreds or thousands of galaxies).

Ellipticals

___________ are in halo within 100,000 ly from the center. Some of them have black holes!

Globular clusters

_______ & _______ stars travel high above and far below the disk on orbits with random orientations

Halo & Bulge

Gravity:

Holds planets in orbit around stars, warps spacetime

_______ hypothesis was that galaxies unwind over time.

Hubble's

Model of galaxy formation: (3 points)

Model: 1. Start with an expanding universe and gas and gravity, and have some regions be denser than others. 2. H, He gas collapses in denser regions (more gravity) to form stars. 3. Gravity pull gas/stars in to create a spinning disk galaxy.

Which Spiral arm to we belong to?

Orion Spiral

What are the two major spiral arms of the MWG?

Perseus Scutum-Centarus

_______ also tells us how much has the universe expanded since the light was emitted towards us.

Redshift

_______ tend to be preferentially found in small groups of galaxies (~few to tens of galaxies) and around voids.

Spirals

How will the universe end?

Suggests a very cold, lonely end, with very few galaxies in sight. The space between bound galaxies will just keep increasing, until we can't even see other galaxies outside the Local Group!

What does expansion mean?

The space between galaxies (the universe itself) is spreading apart.

T/F Expansion implies that the Universe started as a hot, dense. It cooled with time.

True

Inflation

We think a rapid phase of expansion occurred early in the history of the Universe, where it expanded 1030 times in less than 10-36 sec!!

Particles and their ________ can annihilate to create energy!

antiparticles

Older stars are in/between spiral arms

between 95% of stars between spiral arms

Physical Properties of Spirals

blue, star-forming disks low to moderate mass

The radius r of a star's orbit and its velocity v can be used in the formula below to determine m=rv2/g a. mass of star b. mass of MWG c. mass interior to the star's orbit d. mass at center of MWG

c. mass interior to the star's orbit

What are spiral arms made of?

clouds of new stars and debris of earlier generation stars

Amount of _______ is ~25% of the critical density needed to halt expansion. This suggests that the Universe will expand ________.

dark matter, forever

Stars at different distances from the galactic center orbit the galaxy with same/different rates.

different inner more rotations in given time than outer

Where do you find ionization nebulae, blue stars, dust(star formation)? Halo or Disk

disk

_________ starks orbit in circles in the same direction but up & down

disk

galaxies are spinning much slower/faster then they should

faster

Hot, new Universe is pure energy ,________ rays

gamma

Modern model of galaxy evolution is that galaxies form small and grow/shrink over time.

grow

What is the fate of the MWG?

head on collision with Andromeda galaxy

• Strong Force:

holds protons and neutrons together in an atom

_________ _______are found around short-lived (high mass and therefore blue) hot stars signifying active star formation. think where stars are actively formed

ionization nebulae

The late/early Universe was filled with radiation, particles, and antiparticles.

late

•Electromagnetism:

light,electricity,magnets

_______ two similar-sized galaxies makes spheroidal bulges and spheroidal galaxies.

merging

Does the universe have a center or edge?

no

Physical Properties of Ellipticals

old, red & dead spheroids range of sizes: very big (giant, massive) to little (dwarf, low mass)

• Weak Force:

radioactive decay

bubble's discovery all galaxy's spectra are __________.

redshifted

Where does gas go?

returns to interstellar medium Low mass stars blow gas back out into space during the planetary nebula phase as they die. High mass stars blow gas back out into space during the supernova phase as they die. Leaves behind a supernova remnant.

23 _________ are found within the halo. They are losing stars due to MW's disrupting gravitational attraction. Within 100 million years they will cease to exist.

small galaxies

Where does most star formation happen in spiral galaxies?

spiral arms

Gas also gets blown off of massive stars during their lives in the form of _____ ______.

stellar winds

Physical Properties of Irregulars

super star-forming, amorphous low mass

What is the bulge?

the center of galaxy, active & crowded

cosmology

the study of the structure and evolution of the Universe as a whole.

How can we measure rotation curves of spiral galaxies?

using the doppler shift

How are stars in the bulge different from stars in the disk?

yellow, older, random orbits

When we observe distant galaxies we see them as they were when the universe was very young/old

young

What is the Universe made of?

~74% dark energy ~22% dark matter ~4% normal matter

How did galaxies form?

• In the beginning the Universe was filled with hydrogen and helium gas. • Matter was not perfectly uniformly distributed (quantum mechanics!). • In some places it was slightly denser than others (strong observational evidence) • The denser places started contracting under the force of gravity. • In the dense areas gas collapses and forms stars - eventually forms galaxies where star formation continues.

The 4 known forces of nature

•Electromagnetism: Gravity: • Strong Force: holds protons and neutrons together in an atom • Weak Force: radioactive decay