ASTR 104 – Winter 2008 Intersession – Final Exam

Questions on material that we have not covered are greyed out. Blue questions refer to test 3 material.

(1) Why do stars twinkle?
a. Because they are burning spheres of hot gas.
b. Because of their slow motion across the sky.
c. Because of the scattering of starlight caused by Earth's atmosphere.
d. Because sometimes one of their planets passes in front of them.

(2) Does any object rise in the West and set in the East at night?
a. Yes, some stars, called retrograde stars, do.
b. Yes, planets do when they are in retrograde motion.
c. No, celestial objects other than the Sun and Moon do not rise and set.
d. No, celestial objects always rise in the East and set in the West.

(3) What part of the world do we trace the earliest attempts to understand and make models of the Solar System to?
a. Mexico and Central America.
b. Greece and the Middle East.
c. Northern Europe.
d. Southern Africa.

(4) Which of these is the main contribution to astronomy by Tycho Brahe?
a. He made excellent observations of the planets' positions.
b. He proposed a modern heliocentric model of the solar system.
c. He explained the orbits of planets in terms of gravity.
d. He was the first person to use a telescope in astronomy.

(5) Why does an object weigh less on the Moon than on Earth?
a. Because the Moon is very far from the center of the Earth.
b. Because the mass of the object is smaller on the Moon.
c. Because the force of gravity is weaker on the Moon.
d. Because the Moon has no atmosphere.

(6) Which of these types of waves has the longest wavelength?
a. Gamma rays.
b. Visible light.
c. Microwaves.
d. Radio waves.

(7) How many stars does the Solar System contain?
a. None.
b. One.
c. Several thousands.
d. About 100 billion.

(8) What is interesting about the middle star of the handle in the Big Dipper, Mizar?
a. It is a binary star.
b. It is a supergiant star.
c. It is the fastest moving star.
d. It is the brightest star in the sky.

(9) What percentage of its life does a star spend on the main sequence?
a. 10%.
b. 50%.
c. 90%.
d. It varies, some stars never get to the main sequence, other stars never leave it.

(10) Why do astronomers look for supernova explosions in distant galaxies?
a. Because they hope to see signs of life starting to form after the explosion.
b. Because seeing a supernova allows them to find the distance to the galaxy.
c. Because it is interesting to see what happens when a whole galaxy is blown away.
d. Because they are puzzled by the fact that so far they have only been seen in our galaxy.

(11) How massive are neutron stars, compared to the Sun?
a. About 8% of the Sun's mass.
b. About 1.4 to 3 solar masses.
c. About 100 solar masses.
d. Between 0.08 and 100 solar masses.

(12) Which one of the following is a way for black holes to form?
a. A star is surrounded by so much dust that no light can shine through.
b. A star is formed from a cloud of dark matter instead of regular matter.
c. A star collapses to such a small size that its gravity prevents light from escaping.
d. A star cools down past the white dwarf stage and in the end emits no light at all.

(13) What is the most common element in interstellar space?
a. Helium.
b. Carbon.
c. Oxygen.
d. Hydrogen.

(14) Why are certain nebulae dark?
a. Because they are outside our galaxy.
b. Because they are cold and thick, and starlight cannot go through them.
c. Because they have become black holes.
d. Because they are made of a very thin gas which has no effect on light.

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

(16) 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.

(17) Do supernovas occur with single or binary stars?
a. Neither, they have to be in larger clusters.
b. Either one, there are two different types.
c. Single stars.
d. Binary stars.

(18) Which color of light passes more easily through dust in space?
a. Red.
b. Blue.
c. Green.
d. All colors are dimmed by the same amount.

(19) What do we believe is at the center of the Milky Way?
a. We don't have enough information to make a guess.
b. A giant nebula containing 100 billion stars.
c. A black hole of more than two million solar masses.
d. A globular cluster or a supermassive galaxy.

(20) Why do stars swell up to much larger sizes after the main sequence stage in their lives?
a. Because the core grows in size and pushes the other layers outwards.
b. Because what makes them leave the main sequence is often a violent collision.
c. Because the temperature and rate of energy production in the core increase.
d. Because the core shrinks, the layer around it contracts, and it becomes hotter.

(21) What is the Milky Way?
a. A bright reflection nebula contained in the Large Magellanic Cloud.
b. The path followed by the Sun in its motion around the galactic center.
c. The galaxy that the Solar System and the stars around us are located in.
d. A distant galaxy which can be seen in the constellation of Sagittarius.

(22) The speed of light is 300,000 km/s. A spaceship is moving in your direction at 100,000 km/s while you are moving away at 150,000 km/s. If the spaceship shines a beam of light at you, how fast will you see the beam of light moving?
a. 50,000 km/s.
b. 150,000 km/s.
c. 300,000 km/s.
d. 400,000 km/s.

(23) What effect can the shock wave from a supernova explosion have in interstellar space?
a. It can cause a star to collapse and form a black hole.
b. It can trigger the sudden explosion of another massive star.
c. It can trigger star formation in a molecular cloud by compressing it.
d. It can produce a nova by heating up the accretion disk around a white dwarf.

(24) When you look at the sky at night, are the stars you see with the naked eye inside our own galaxy?
a. Yes, all of them are inside our galaxy.
b. No, each of those stars is inside its own galaxy.
c. Some of them are, but most belong to different galaxies.
d. No, stars are not actually inside the galaxy, they orbit around it.

(25) 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.

(26) Why are right ascension and declination better than altitude and azimuth for specifying the location of a star?
a. Because right ascension and declination can be predicted more accurately.
b. Because right ascension and declination take the star's parallax into account.
c. Because altitude and azimuth change with the location on Earth and in time.
d. Because altitude and azimuth are old-fashioned and their meaning is not very clear.

(27) How hot are the surfaces of the hottest stars, approximately?
a. 300 K.
b. 5000 K.
c. 50,000 K.
d. 200 million K.

(28) How did people first figure out how far the Andromeda galaxy is?
a. By spotting bright Cepheid variable stars in it.
b. By watching a supernova explosion inside it.
c. By using the parallax method and the HR diagram.
d. By finding its velocity and using Hubble's law.

(29) What does the angular resolution tell you about a telescope?
a. Its ability to detect fine detail and produce sharp images.
b. The number of spectral lines one can see with it.
c. Its ability to produce bright images of faint objects.
d. The magnification of the images it produces.

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

(31) As we observe beyond a certain distance from us, we start to see no more galaxies. How is this possible?
a. There are too many clouds of gas and dust in between.
b. We are looking back in time to when galaxies first started forming.
c. Beyond that distance all galaxies become too faint.
d. Beyond that distance there is just empty space with no more galaxies.

(32) Why didn't ancient astronomers see parallax for the stars?
a. Because the Earth's motion prevents us from seeing the parallax.
b. Because stars are so distant that one needs a telescope to see their parallax.
c. Because they incorrectly thought that they were seeing retrograde motion instead.
d. Because they didn't know that one can see parallax only on certain days of the year.

(33) Approximately how far from us is the Andromeda galaxy, M31?
a. 2 light years.
b. 2,000 light years.
c. 2 million light years.
d. 2 billion light years.

(34) 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.

(35) According to Kepler's laws, the orbit of a planet is:
a. A perfect circle, with the Sun at the center.
b. An ellipse, with the Sun at the center.
c. A circle, with smaller circles added in to account for detailed observations.
d. An ellipse, with the Sun at one of the foci.

(36) What are the Magellanic Clouds?
a. Large clouds of gas and dust near the center of the Milky Way.
b. Smaller clouds of dust near the Trapezium inside the Orion nebula.
c. Two small irregular galaxies near the Milky Way.
d. The two largest galaxies in the Local Group.

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

(38) What happens inside an atom when it absorbs a photon?
a. The nucleus becomes hotter and expands.
b. An electron jumps from a lower energy state to a higher one.
c. One more electron is added to the atom.
d. All electrons start moving faster along their orbits.

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

(40) 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.

(41) If a thin gas is heated to thousands of degrees, one obtains from it
a. An emission line spectrum.
b. An absorption line spectrum.
c. A continuous emission spectrum.
d. A continuous absorption spectrum.

(42) What is the main evidence we have that the universe started with a hot big bang?
a. The cosmic microwave background.
b. The presence of dark matter.
c. The age of globular clusters in our galaxy.
d. The fact that the cores of many galaxies are still burning.

(43) 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.

(44) How do the planets in the outer Solar System compare to Earth?
a. They all orbit around the Sun in the opposite direction.
b. Them are all much larger than the Earth.
c. They are all smaller than the Earth.
d. They are about the same size, but they have rings instead of a moon.

(45) How are people trying to find out if extrasolar planets have atmospheres?
a. Measure the rotation of the planet.
b. Look for a Doppler shift in light coming from the planet.
c. Measure the mass of the planet.
d. Look for absorption lines in starlight passing near the planet.

(46) How many extrasolar planets have we discovered so far?
a. None, but technology will soon reach a point where we will find them.
b. Two, they have just been discovered last year by the Hubble Telescope.
c. More than 200 have been reported, and the list keeps growing.
d. Thousands; every star that has been carefully checked has planets.

(47) By how much do stars move on the celestial sphere over time?
a. They move about a degree per day, that is why summer and winter constellations are different.
b. They are constantly moving, that is why they rise in the East and set in the West every day.
c. They hardly move, at most by a few arcsecond per year, and usually it takes years to notice.
d. Stars do not move on the celestial sphere, only planets do.

(48) How long after the Big Bang did the first stars and galaxies form?
a. Three minutes.
b. 300,000 years.
c. Several hundred million years.
d. 13.7 billion years.

(49) How can we find neutron stars?
a. If they are not surrounded by glowing matter there is no way for us to see them.
b. They can often be seen as pulsars, from which we get pulses of radio waves.
c. We recognize them because they shine more brightly than any other regular star.
d. We look for stars whose brightness changes over a period of a few days.

(50) How many stars do open clusters usually have?
a. Between 2 and 5.
b. A dozen or so.
c. A few hundreds or thousands.
d. Hundreds of thousands or more.

(51) What is an epicycle?

(52) What is the Big Bang?

(53) How can we find the distance to the nearest stars?

(54) Explain very briefly one method that has been successful in the search for extrasolar planets.

(55) What is the Local Group?

(56) Name one prediction of Einstein’s theory of gravity that was not part of Newton’s theory of gravity.

(57) What is a galaxy?

(58) What is a nebula?

(59) Do the objects in the room around you emit any radiation? (If yes, what type? If no, how do you know?)

(60) What is the solution of Olbers’ paradox?

(61) A 2007 TV news report said that "Pictures of the star Mira, a red giant similar to what the Sun will be like near the end of its life, have shown that it has a tail, several light-years long, of material it has been ejecting over many thousands of years while moving across a distant galaxy". What is wrong with the statement?