ASTR 101 – Practice Final Exam (Fall 2012 Final)
(for the correct answers, click on the link at the bottom of the page)

Multiple-choice questions (circle the letter next to your choice of answer, but do not write the letter next to the question)

(1) The study of the structure and evolution of the universe as a whole is called
a. Ornitology.
b. Astrology.
c. Cosmology.
d. Cosmetology.

(2) Where is the center of the universe?
a. At the center of the Milky Way.
b. Near the middle of the Virgo cluster.
c. There is no center, if our current ideas are correct.
d. We don't know exactly, but probably near the Great Attractor.

(3) Suppose a star is 10,000 light years away. Which one of the following could it possibly belong to?
a. The Solar System.
b. The Milky Way Galaxy.
c. The Andromeda Galaxy.
d. The Virgo Cluster.

(4) Does the Sun orbit around anything?
a. No, planets orbit around the Sun.
b. Yes, the Earth.
c. Yes, the center of our galaxy.
d. Yes, the center of the universe.

(5) Can we see planets orbiting around other stars with our telescopes?
a. Yes, they show up as smaller bright dots next to their stars.
b. Yes, we see them as dark spots when they pass in front of their stars.
c. Not yet, but with better telescopes we may soon be able to see them.
d. No, there is no hope to ever see them because they do not emit light.

(6) What part of our galaxy are we located in?
a. The core.
b. The bulge.
c. The disk.
d. The halo.

(7) Why do we believe that our galaxy contains a large amount of dark matter?
a. Because the light coming from distant stars is unusually dim.
b. Because we cannot see the center of the galaxy from here.
c. Because of how fast most stars move around the galactic center.
d. Because of the large number of black holes we see in the galaxy.

(8) What appears to be the most likely scenario for the future of the universe?
a. It will probably keep expanding forever.
b. It will eventually recollapse away to a point.
c. It will eventually all fall into a single black hole.
d. It will keep expanding and contracting in cycles.

(9) Why can't we see what is near the center of our galaxy with regular optical telescopes?
a. Because at night we don't face the right direction to point our telescopes there.
b. Because there is too much gas and dust there for visible light to go through.
c. Because it is so far away that light has not had time to reach us yet.
d. Because there is a black hole there that doesn't let any light escape.

(10) Approximately how wide is our galaxy?
a. 10 light years.
b. 1000 light years.
c. 100,000 light years.
d. 2 million light years.

(11) Approximately how long does it take for our galaxy to rotate once?
a. About 2,200 years.
b. About 100,000 years.
c. About 220 million years.
d. About 10 billion years.

(12) Are all galaxies moving away from us?
a. Yes.
b. No, all distant galaxies do, but some nearby ones do not.
c. No, all nearby galaxies do, but the distant ones do not.
d. No, elliptical galaxies do, but spiral galaxies don't.

(13) How long after the beginning of the universe did the first stars and galaxies form?
a. A few seconds.
b. Three minutes.
c. 300,000 years.
d. Several hundred million years.

(14) What is Olbers' paradox?
a. The fact that the night sky is dark rather than bright.
b. The fact that the universe is still expanding after so long.
c. The fact that there is so much dark matter in the universe.
d. The fact that such a large universe could have come from a point.

(15) How do the planets we have discovered so far around other stars differ from the solar ones?
a. Most of them are smaller than the solar planets.
b. Most of them are larger than the solar planets.
c. They don't all revolve in the same direction around their star.
d. Most of them are wandering in space, instead of orbiting a star.

(16) Why did ordinary atoms form only many years after the Big Bang?
a. Because before then there was no matter in the universe.
b. Because it took that long for the universe to cool down enough.
c. Because before then protons and electrons repelled each other.
d. Because stars are needed for atoms to be able to form.

(17) How can we find the distance to a nearby galaxy, like Andromeda?
a. We use the parallax method.
b. We find its temperature and use the HR diagram.
c. We look for variable stars such as Cepheids in it.
d. We find its velocity and use Hubble's law.

(18) How far from the center of our galaxy are we?
a. About 4 light years.
b. About 28,000 light years.
c. About 2 million light years.
d. About 25 billion light years.

(19) What is an extrasolar planet?
a. A planet that does not orbit around a star.
b. A planet that orbits around two stars (it has an extra star).
c. A planet that is outside the solar system (it does not orbit our Sun).
d. A planet that used to orbit the Sun but has now left our galaxy.

(20) Do planets affect the motion of the stars they orbit?
a. No, it is the other way around, stars make the planets go around in orbits.
b. No, stars only move in orbits around the center of the galaxy.
c. Yes, planets cause stars to slow down in their motion around the galaxy.
d. Yes, stars also feel a gravitational pull from planets, but they move much less.

(21) Where did the cosmic microwave radiation that fills the universe come from?
a. The explosion of the first generation of massive star supernovas.
b. The light produced by particles before atoms were formed in the hot early universe.
c. Charged particles moving in the intense magnetic fields of some black holes.
d. All the nebulas in all the galaxies we see today in the universe combined.

(22) What is at the exact center of our galaxy?
a. The Milky Way.
b. The Solar System.
c. A massive black hole.
d. The Virgo Cluster.

(23) Do we know of the existence of planets around stars outside our Solar System?
a. No, the Sun is the only star that has known planets around it.
b. We don't know yet, but many astronomers think there are.
c. Yes, more than 700 are already known, and the list keeps growing.
d. Yes, all stars have planets. One star we know has about 180.

(24) What is a normal value for the distance between neighboring galaxies?
a. A few thousand light years.
b. A few thousand astronomical units.
c. A few millions of light years.
d. A few millions of astronomical units.

(25) What is the difference between dark matter and dark energy?
a. Dark matter tends to slow down the expansion of the universe, dark energy speeds it up.
b. Dark matter is matter that fell into a black hole, dark energy travels at the speed of light.
c. Dark matter absorbs all types of light, dark energy only specific wavelengths.
d. Nothing, they are two expressions for the same concept.

(26) What is dark matter?
a. The matter out of which black holes are made.
b. Matter whose gravity repels rather than attracting.
c. Clouds of dust responsible for the fact that the sky is dark at night.
d. Matter that we detect only by its gravitational pull on other objects.

(27) Three astronomical objects are called M51, M54 and M57. None of these can be:
a. A comet.
b. A galaxy.
c. A globular cluster.
d. A bright nebula.

(28) Which two quantities are related according to Hubble's law?
a. A galaxy's brightness and its rotation.
b. A galaxy's rotation and its speed.
c. A galaxy's speed and its distance.
d. A galaxy's distance and its brightness.

(29) How do the contents of the halo and disk of our galaxy differ?
a. The halo has more dust and young stars than the disk.
b. The disk has dust and young stars, the halo doesn't.
c. The halo is round because it spins, the disk does not spin.
d. The disk has dark matter, the halo doesn't.

(30) According to the standard theory, how long has the universe existed?
a. 13,700 years.
b. 13.7 million years.
c. 13.7 billion years.
d. 13,700 billion years.

(31) What is a galaxy?
a. A cloud of interstellar gas and dust at least 10 light years across.
b. A cluster of stars which contains more than 100 stars.
c. A star, together with all of its planets and surrounding matter disk.
d. A collection of millions or billions of stars bound together by gravity.

(32) Which of the following is not one of the main types of galaxies?
a. Spiral galaxy.
b. Elliptical galaxy.
c. Globular galaxy.
d. Irregular galaxy.

(33) What type of galaxy is the Milky Way?
a. Spiral.
b. Elliptical.
c. Globular.
d. Irregular.

(34) How many galaxies are there in the Solar System?
a. That's a silly question, it's the Solar System that is inside a galaxy.
b. An infinite number, according to our current understanding.
c. About 100 billion.
d. One.

(35) Can we measure the speed at which galaxies move?
a. Yes, using precision astrometry we can watch thir position change over many years.
b. Yes, from their redshift or blueshift we can find their speed towards or away from us.
c. We could, like we do for stars, but actually we would find that galaxies don't move.
d. No, they are much too far away.

(36) According to current ideas, what is the universe composed of, approximately?
a. 95% regular matter, 5% dark matter.
b. 10% regular matter, 90% dark energy.
c. 5% regular matter, 5% dark energy, 90% dark matter.
d. 4% regular matter, 22% dark matter, 74% dark energy.

(37) How can we find out the distances to the farthest galaxies?
a. We use the spectroscopic parallax method.
b. We look for variable stars such as Cepheids in them.
c. We send a signal, and record the time it takes for it to come back.
d. We find the speed at which they move away and use Hubble's law.

(38) Which of the following do the Magellanic Clouds belong to?
a. In the Solar System.
b. In the Pleiades Cluster.
c. In the Local Group.
d. In the Virgo Cluster.

(39) Have astronomers located all the galaxies in the observable universe?
a. No, no galaxy other than our own has actually been seen so far.
b. No, there are way too many and only a few sections of the sky have been studied in detail.
c. We are close, we expect that within the next couple of years all locations will be mapped.
d. Yes, a full survey of all observable galaxies has just been completed.

(40) If you go out on a dark moonless night and see thousands of stars with your naked eyes, those stars are
a. A very small part of the Solar System.
b. A very small part of our galaxy.
c. All of the stars in our galaxy.
d. Stars belonging to many different galaxies.

Short-answer questions (I expect answers to be about 1-2 lines long, but do not write answers longer than 3 lines)

(1) If you see a bright point of light in the sky, how can you tell whether it is a planet or a star? (Without help from a star chart, planetarium software, or anything like that!)

(2) How long does a star like the Sun live, and what will happen to it in the end?

(3) Which planets can occasionally be seen transiting the Sun, and why?

(4) Name one place in the solar system, other than Mars (and Earth!) that is considered as a possibility for forms of life to exist or have existed on, and briefly state why.

(5) How can we find out how hot a star is?

(6) What is the most common and successful method to search for extrasolar planets?

(7) What is the reason why we have seasons on Earth?

(8) What was Copernicus' main contribution to astronomy?

(9) What are the Pleiades, sometimes also known as the "Seven Sisters"?

(10) From the point of view of astronomy, what distinguishes the Zodiac constellations from the other ones?

(11) What is Ceres?

(12) Briefly describe one way in which a supernova explosion can happen.

(13) Why are most asteroids not round like planets are?

(14) What is a black hole?

(15) What do we mean by angular resolution of a telescope, and what is the main thing to do to improve it?

(16) Name one feature that distinguishes Saturn from all other planets, and briefly describe it.

(17) What does it mean to say that a star system is an eclipsing binary?

(18) What is the Big Bang?

(19) Which planets (other than Earth!) have spacecraft landed on?

Answers