ASTRO 105 EXAM 2 REVIEW - ANSWERS BELOW

AST 105               Review for Exam #2    Fall 2003

MULTIPLE CHOICE.  Choose the one alternative that best completes the statement or answers the question.

1)  The allowed shapes for orbits under the force of gravity are

A) ellipses only.

B) ellipses and spirals.

C) ellipses, parabolas, and hyperbolas.

D) ellipses, spirals, and parabolas.

E) spirals, circles, and squares.

2)  Thermal radiation is defined as

A) radiation produced by a hot object.

B) radiation in the infrared part of the spectrum.

C) radiation that depends only on the emitting object's temperature.

D) radiation in the form of emission lines from an object.

E) radiation that is felt as heat.

3)  You observe a distant galaxy. You find that a spectral line normally found in the visible

part of the spectrum is shifted toward the infrared. What do you conclude?

A) The galaxy is moving away from you.

B) The galaxy is moving toward you.

C) The galaxy has very weak gravity.

D) The galaxy is made purely of hydrogen.

E) The composition of the galaxy is changing.

4)  Newton's second law of motion tells us that the net force applied to an object equals its

A) mass times energy.

B) momentum times velocity.

C) mass times velocity.

D) energy times acceleration.

E) mass times acceleration.

5)  Which of the following could not be determined by an observation that uses only

spectroscopy?

A) the chemical composition of a distant star

B) the speed at which a distant galaxy is moving away from us

C) the surface temperature of a distant star

D) the rotation rate of a distant star

E) the size of a distant galaxy

6)  Without telescopes or other aid, we can look up and see the Moon in the night sky because it

A) emits visible light.

B) emits thermal radiation.

C) reflects infrared light.

D) reflects visible light.

E) glows through radioactive decay.

7)  When an electron in an atom goes from a higher energy state to a lower energy state, the

     atom

A) emits a photon of a specific frequency.

B) absorbs a photon of a specific frequency.

C) absorbs several photons of a specific frequency.

D) can emit a photon of any frequency.

E) can absorb a photon of any frequency.

8)  You are standing on a scale in an elevator. Suddenly you notice your weight decreases. What do you conclude?

A) The elevator is accelerating upwards.

B) The elevator is moving at a constant velocity upwards.

C) The elevator is accelerating downwards.

D) The elevator is moving at a constant velocity downwards.

E) Your diet is working.

9)  Which of the following is an example in which you are traveling at constant speed but not at constant velocity?

A) rolling freely down a hill in a cart, traveling in a straight line

B) driving backward at exactly 50 km/hr

C) driving around in a circle at exactly 100 km/hr

D) jumping up and down, with a period of exactly 60 hops per minute

E) none of the above

10)  Suppose you see two stars: a blue star and a red star. Which of the following can you conclude about the two stars? Assume that no Doppler shifts are involved. (Hint: Think about the laws of thermal radiation.)

A) The red star is more massive than the blue star.

B) The blue star is more massive than the red star.

C) The blue star is farther away than the red star.

D) The blue star has a hotter surface temperature than the red star.

E) The red star has a hotter surface temperature than the blue star.

11)  What quantities does angular momentum depend upon?

A) mass and velocity

B) mass, velocity, and radius

C) force and radius

D) force, velocity, and radius

E) momentum and angular velocity

12)  How are wavelength, frequency, and energy related for photons of light?

A) Longer wavelength means lower frequency and lower energy.

B) Longer wavelength means higher frequency and lower energy.

C) Longer wavelength means higher frequency and higher energy.

D) Longer wavelength means lower frequency and higher energy.

E) There is no simple relationship because different photons travel at different speeds.

13)  When an atom absorbs a photon containing energy, any of the following can happen

except which?

A) The atom becomes excited.

B) The atom is ionized.

C) An electron moves from an upper energy level to a lower one.

D) An electron moves from a lower energy level to an upper one.

14)  From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?

A) infrared, visible light, ultraviolet, X rays, gamma rays, radio

B) radio, infrared, visible light, ultraviolet, X rays, gamma rays

C) visible light, infrared, X rays, ultraviolet, gamma rays, radio

D) gamma rays, X rays, ultraviolet, visible light, infrared, radio

E) gamma rays, X rays, visible light, ultraviolet, infrared, radio

15)  When an atom loses an electron, it becomes

A) sublimated.

B) dissociated.

C) ionized.

D) an isotope.

E) a plasma.

16)  Suppose an object is moving in a straight line at 50 mi/hr. According to Newton's first law of motion, the object will

A) continue to move in the same way forever, no matter what happens.

B) continue to move in the same way until it is acted upon by a force.

C) eventually slow down and come to a stop.

D) continue to move in a straight line forever if it is in space, but fall to the ground if it is on

Earth.

17)  Which of the following statements about X rays and radio waves is not true?

A) Neither X rays nor radio waves can penetrate the Earth's atmosphere.

B) X rays have shorter wavelengths than radio waves.

C) X rays and radio waves are both forms of light, or electromagnetic radiation.

D) X rays have higher frequency than radio waves.

E) X rays have higher energy than radio waves.

18)  The spectra of most galaxies show redshifts. This means that their spectral lines

A) always are in the red part of the visible spectrum.

B) have wavelengths that are longer than normal.

C) have wavelengths that are shorter than normal.

D) have a higher intensity in the red part of the spectrum.

E) have normal wavelengths, but absorption of light makes them appear red.

19)  How can an electron in an atom lose energy to go from a higher energy level to a lower energy level?

A) It loses kinetic energy.

B) It releases a photon equal in energy to its own energy drop.

C) It absorbs a photon equal in energy to its own energy drop.

D) It loses gravitational potential energy.

E) It exchanges gravitational potential energy for kinetic energy.

20)  If your mass is 60 kg on Earth, what would your mass be on the Moon?

A) 10 lb B)  10 kg C)  50 kg D)  60 kg E)  60 lb

21)  Momentum is defined as

A) mass times speed.

B) mass times velocity.

C) force times velocity.

D) mass times acceleration.

E) force times acceleration.

22)  According to the universal law of gravitation, the force due to gravity is

A) directly proportional to the square of the distance between objects.

B) inversely proportional to the square of the distance between objects.

C) directly proportional to the distance between objects.

D) inversely proportional to the distance between objects.

E) not dependent on the distance between objects.

23)  Grass (that is healthy) looks green because

A) it emits green light and absorbs other colors.

B) it absorbs green light and emits other colors.

C) it transmits green light and emits other colors.

D) it reflects green light and absorbs other colors.

24)  From laboratory measurements, we know that a particular spectral line formed by hydrogen appears at a wavelength of 486.1 nanometers (nm). The spectrum of a particular star shows the same hydrogen line appearing at a wavelength of 485.9 nm. What can we conclude?

A) The star is moving toward us.

B) The star is moving away from us.

C) The star is getting hotter.

D) The star is getting colder.

E) The "star" actually is a planet.

25)  The frequency of a wave is

A) the number of peaks passing by any point each second.

B) measured in cycles per second.

C) measured in hertz (Hz).

D) equal to the speed of the wave divided by the wavelength of the wave.

E) all of the above.

1)  Answer:  C

2)  Answer:  C

3)  Answer:  A

4)  Answer:  E

5)  Answer:  E

6)  Answer:  D

7)  Answer:  A

8)  Answer:  C

9)  Answer:  C

10)  Answer:  D

11)  Answer:  B

12)  Answer:  A

13)  Answer:  C

14)  Answer:  D

15)  Answer:  C

16)  Answer:  B

17)  Answer:  A

18)  Answer:  B

19)  Answer:  B

20)  Answer:  D

21)  Answer:  B

22)  Answer:  B

23)  Answer:  D

24)  Answer:  A

25)  Answer:  E

ASTRO 105 REVIEW FINAL - ANSWERS BELOW

MULTIPLE CHOICE.  Choose the one alternative that best completes the statement or answers the question.

1)  Which two energy sources can help a star maintain its internal thermal pressure?

A) nuclear fusion and gravitational contraction

B) nuclear fission and gravitational contraction

C) nuclear fusion and nuclear fission

D) chemical reactions and gravitational contraction

E) nuclear fusion and chemical reactions

2)  What happens to the core of a star after a planetary nebula occurs?

A) It contracts from a protostar to a main-sequence star.

B) It breaks apart in a violent explosion.

C) It becomes a white dwarf.

D) It becomes a neutron star.

E) none of the above

3)  Compared to the star it evolved from, a white dwarf is

A) hotter and brighter.

B) hotter and dimmer.

C) cooler and brighter.

D) cooler and dimmer.

E) the same temperature and brightness.

4)  What happens when the gravity of a massive star is able to overcome neutron degeneracy pressure?

A) The core contracts and becomes a white dwarf.

B) The core contracts and becomes a ball of neutrons.

C) The core contracts and becomes a black hole.

D) The star explodes violently, leaving nothing behind.

E) Gravity is not able to overcome neutron degeneracy pressure.

5)  Which of the following statements about stages of nuclear burning (i.e., first-stage hydrogen burning, second-stage helium burning, etc.) in a massive star is not true?

A) Each successive stage of fusion requires higher temperatures than the previous stages.

B) As each stage ends, the core shrinks further.

C) Each successive stage creates an element with a higher atomic weight.

D) Each successive stage lasts for approximately the same amount of time.

6)  Which event marks the beginning of a supernova?

A) the onset of helium burning after a helium flash in a star with mass comparable to that of the Sun

B) the sudden outpouring of X rays from a newly formed accretion disk

C) the sudden collapse of an iron core into a compact ball of neutrons

D) the beginning of neon burning in an extremely massive star

E) the expansion of a low-mass star into a red giant

7)  Why is Supernova 1987A particularly important to astronomers?

A) It occurred only a few dozen light-years from Earth.

B) It provided the first evidence that supernovae really occur.

C) It provided the first evidence that neutron stars really exist.

D) It was the first supernova detected in nearly 400 years.

E) It was the nearest supernova detected in nearly 400 years.

8)  White dwarfs are so called because

A) the are both very hot and very small.

B) they are the end-products of small, low-mass stars.

C) they are the opposite of black holes.

D) it amplifies the contrast with red giants.

E) they are supported by electron degeneracy pressure.

9)  Which of the following is closest in mass to a white dwarf?

A) the Moon B)  the Earth C)  Jupiter D)  the Sun

10)  Suppose a white dwarf is gaining mass because of accretion in a binary system. What

       happens if the mass someday reaches the 1.4-solar-mass limit?

A) The white dwarf undergoes a catastrophic collapse, leading to a type of supernova that is somewhat different from that which occurs in a massive star but is comparable in energy.

B) The white dwarf, which is made mostly of carbon, suddenly becomes much hotter in temperature and therefore is able to begin fusing the carbon. This turns the white dwarf back into a star supported against gravity by ordinary pressure.

C) The white dwarf immediately collapses into a black hole, disappearing from view.

D) A white dwarf can never gain enough mass to reach the limit because a strong stellar wind prevents the material from reaching it in the first place.

11)  What kind of pressure supports a white dwarf?

A) neutron degeneracy pressure

B) electron degeneracy pressure

C) thermal pressure

D) radiation pressure

E) all of the above

12)  After a massive star supernova, what is left behind?

A) always a white dwarf

B) always a neutron star

C) always a black hole

D) either a white dwarf or a neutron star

E) either a neutron star or a black hole

13)  From an observational standpoint, what is a pulsar?

A) a star that slowly changes its brightness, getting dimmer and then brighter with a period

     of anywhere from a few hours to a few weeks

B) an object that emits flashes of light several times per second or more, with near perfect

    regularity

C) an object that emits random "pulses" of light that sometimes occur only a fraction of a

     second apart and other times stop for several days at a time

D) a star that changes color rapidly, from blue to red and back again

14)  What causes the radio pulses of a pulsar?

A) The star vibrates.

B) As the star spins, beams of radio radiation sweep through space. If one of the beams crosses

     the Earth, we observe a pulse.

C) The star undergoes periodic explosions of nuclear fusion that generate radio emission.

D) The star's orbiting companion periodically eclipses the radio waves emitted by the main

      pulsar.

E) A black hole near the star absorbs energy and re-emits it as radio waves.

15)  How does a black hole form from a massive star?

A) During a supernova, if a star is massive enough for its gravity to overcome neutron

     degeneracy of the core, the core will be compressed until it becomes a black hole.

B) Any star that is more massive than 8 solar masses will undergo a supernova explosion and

     leave behind a black-hole remnant.

C) If enough mass is accreted by a white-dwarf star so that it exceeds the 1.4-solar-mass limit, it

     will undergo a supernova explosion and leave behind a black-hole remnant.

D) If enough mass is accreted by a neutron star, it will undergo a supernova explosion and leave

     behind a black-hole remnant.

E) A black hole forms when two massive main-sequence stars collide.

16)  What do we mean by the singularity of a black hole?

A) There are no binary black holes     each one is isolated.

B) An object can become a black hole only once, and a black hole cannot evolve into anything

     else.

C) It is the center of the black hole, a place of infinite density where the known laws of physics

     cannot describe the conditions.

D) It is the edge of the black hole, where one could leave the observable universe.

E) It is the "point of no return" of the black hole; anything closer than this point will not be

    able to escape the gravitational force of the black hole.

17)  If you were to come back to our Solar System in 6 billion years, what might you expect

       to find?

A) a red giant star

B) a white dwarf

C) a rapidly spinning pulsar

D) a black hole

E) Everything will be pretty much the same as it is now.

18)  What kinds of objects lie in the disk of our galaxy?

A) open clusters

B) O and B stars

C) old K and M stars

D) gas and dust

E) all of the above

19)  Harlow Shapley concluded that the Sun was not in the center of the Milky Way Galaxy by

A) looking at the shape of the "milky band" across the sky.

B) mapping the distribution of stars in the galaxy.

C) mapping the distribution of globular clusters in the galaxy.

D) mapping the distribution of gas clouds in the spiral arms.

E) looking at other nearby spiral galaxies.

20)  All the iron on Earth originated from

A) white dwarfs.

B) nuclear fusion within the cores of low-mass stars.

C) nuclear fusion within the cores of high-mass stars.

D) the Big Bang, when the universe first began.

E) the bombardment of comets in the late stages of planet formation.

21)  What is the most common form of gas in the interstellar medium?

A) molecular hydrogen

B) molecular helium

C) atomic hydrogen

D) atomic helium

E) ionized hydrogen

22)  Compared with our Sun, most stars in the halo are

A) young, red, and dim and have fewer heavy elements.

B) young, blue, and bright and have much more heavy element material.

C) old, red, and dim and have fewer heavy elements.

D) old, red, and dim and have much more heavy element material.

E) old, red, and bright and have fewer heavy elements.

23)  Which types of galaxies have a clearly defined spheroidal component?

A) spirals only

B) ellipticals only

C) lenticulars only

D) irregulars only

E) all but irregulars

24)  How does a lenticular galaxy differ from a normal spiral galaxy?

A) It has no bulge.

B) It has an elongated bulge resembling a bar more than a sphere.

C) It is flatter in shape.

D) It has no gas or dust.

E) It has no spiral arms.

25)  Why are Cepheid variables important?

A) Cepheid variables are stars that vary in brightness because they harbor a black hole.

B) Cepheids are pulsating variable stars, and their pulsation periods are directly related to

     their true luminosities. Hence, we can use Cepheids as "standard candles" for distance

     measurements.

C) Cepheids are a type of young galaxy that helps us understand how galaxies form.

D) Cepheids are supermassive stars that are on the verge of becoming supernovae and therefore allow us to choose candidates to watch if we hope to observe a supernova in the near future.

26)  How was Edwin Hubble able to use his discovery of a Cepheid in Andromeda to prove

       that the "spiral nebulae" were actually entire galaxies?

A) There are no Cepheids in the Milky Way, so his discovery proved that it had to be in another        galaxy.

B) He measured the stellar parallax of the Cepheid in Andromeda, was able to determine the

     distance to it, and showed that it was far outside the Milky Way Galaxy.

C) He used main-sequence fitting to determine the distance to Andromeda and show that it was     far outside the Milky Way Galaxy.

D) From the period-luminosity relation for Cepheids, he was able to determine the distance to

     Andromeda and show that it was far outside the Milky Way Galaxy.

E) Since a Cepheid is a type of luminous galaxy, when he found it in Andromeda he was able to

     prove that Andromeda was a separate galaxy from the Milky Way.

27)  What is Hubble's law?

A) The longer the time period between peaks in brightness, the greater the luminosity of the

     Cepheid variable star.

B) The recession velocity of a galaxy is directly proportional to its distance from us.

C) The recession velocity of a galaxy is inversely proportional to its distance from us.

D) The faster a spiral galaxy's rotation speed, the more luminous it is.

E) The faster a spiral galaxy's rotation speed, the less luminous it is.

28)  What is the primary practical difficulty that limits the use of Hubble's law for measuring

       distances?

A) Redshifts of galaxies are difficult to measure.

B) The recession velocities of distant galaxies are so great that they are hard to measure.

C) We do not know Hubble's constant very accurately yet.

D) Hubble's law is only useful theoretically; it is difficult to use in practice.

E) The motion of the Earth relative to the Milky Way is difficult to account for.

29)  How do observations of distant galaxies help us learn about galaxy evolution?

A) Observations at different distances show galaxies of different ages and therefore different

      stages of evolution.

B) We can observe the birth of galaxies.

C) We can observe the evolution of a single galaxy over time.

D) We can observe two galaxies merging and what the result is, helping us learn how mergers

      affect evolution.

E) We can see what our galaxy used to look like and therefore theorize about the physical

     processes that led to its current appearance.

30)  What is a quasar?

A) a starlike object that actually represents a bright patch of gas in the Milky Way

B) a very large galaxy thought to be formed by the merger of several smaller galaxies,

     typically found in the center of a galaxy cluster

C) a specialized astronomical instrument for observing distant stars.

D) the extremely bright center of a distant galaxy, thought to be powered by a massive black

     hole

E) another name for very bright stars of spectral type O

1)  Answer:  A

2)  Answer:  C

3)  Answer:  B

4)  Answer:  C

5)  Answer:  D

6)  Answer:  C

7)  Answer:  E

8)  Answer:  A

9)  Answer:  D

10)  Answer:  A

11)  Answer:  B

12)  Answer:  E

13)  Answer:  B

14)  Answer:  B

15)  Answer:  A

16)  Answer:  C

17)  Answer:  B

18)  Answer:  E

19)  Answer:  C

20)  Answer:  C

21)  Answer:  C

22)  Answer:  C

23)  Answer:  E

24)  Answer:  E

25)  Answer:  B

26)  Answer:  D

27)  Answer:  B

28)  Answer:  C

29)  Answer:  A

30)  Answer:  D

ASTRO 105 REVIEW 3 - ANSWERS BELOW

MULTIPLE CHOICE.  Choose the one alternative that best completes the statement or answers the question.

1)  What is differentiation in planetary geology?

A) the process by which gravity separates materials according to density

B) the process by which different types of minerals form a conglomerate rock

C) any process by which a planet's surface evolves differently from another planet's surface

D) any process by which one part of a planet's surface evolves differently from another part of the same planet's surface

E) any process by which a planet evolves differently from its moons

2)  Heat escapes from the planet's surface into space by thermal radiation. Planets radiate

    almost entirely in the wavelength range of the

A) infrared.

B) radio.

C) visible.

D) ultraviolet.

E) none of the above

3)  What are the conditions necessary for a terrestrial planet to have a strong magnetic field?

A) a molten metallic core only

B) fast rotation only

C) a rocky mantle only

D) both a molten metallic core and reasonably fast rotation

E) both a metal core and a rocky mantle

4)  A planet is most likely to have tectonic activity if it has

A) low surface gravity.

B) high surface gravity.

C) low internal temperature.

D) high internal temperature.

E) a dense atmosphere.

5)  Olympus Mons is a

A) shield volcano on Mars.

B) stratovolcano on Mercury.

C) large lava plain on the Moon.

D) shield volcano on Venus.

E) stratovolcano on the Moon.

6)  Which of the following worlds has the most substantial atmosphere?

A) Mercury B)  Venus C)  the Moon D)  Mars E)  Earth

7)  What is the troposphere?

A) the lowest layer in the atmosphere

B) the part of the atmosphere that absorbs optical light

C) the part of the atmosphere that absorbs ultraviolet

D) the part of the atmosphere that absorbs X-rays

E) the highest layer in the atmosphere

8)  Why are there no impact craters on the surface of Io?

A) It is too small to have been bombarded by planetesimals in the early solar system.

B) Jupiter's strong gravity attracted the planetesimals more strongly than Io and thus none

     landed on its surface.

C) Io did have impact craters but they have all been buried in lava flows.

D) Any craters that existed have been eroded through the strong winds on Io's surface.

E) Io's thick atmosphere obscures the view of the craters.

9)  What is Jupiter's Great Red Spot?

A) the place where reddish particles from Io impact Jupiter's surface

B) a hurricane that comes and goes on Jupiter

C) a large mountain peak poking up above the clouds

D) a long\'2Dlived, high\'2Dpressure storm

E) the place where Jupiter's aurora is most visible

10)  What is a Roche zone?

A) a bright layer of gas on Jupiter

B) the region near a planet where tidal forces would tear apart an object held together only by

    gravity

C) the region within a planet's magnetic field where charged particles accumulate

D) the region surrounding a planet where it may have large moons

E) a region where gravitational resonances clear a gap in a planet's rings

11)  Which of the Jovian planets have rings?

A) Jupiter

B) Saturn

C) Uranus

D) Neptune

E) all of the above

12)  An icy leftover planetesimal orbiting the Sun is

A) a comet.

B) a meteor.

C) an asteroid.

D) a meteorite.

E) possibly any of the above.

13)  A typical shooting star in a meteor shower is caused by a __________ entering the Earth's

       atmosphere.

A) boulder-size particle from an asteroid

B) boulder-size particle from a comet

C) pea-size particle from an asteroid

D) pea-size particle from a comet

E) microscopic particle of interstellar dust

14)  Why does the plasma tail of a comet always point away from the Sun?

A) The solar wind blows the ions directly away from the Sun.

B) Radiation pressure from the Sun's light pushes the ions away.

C) The conservation of the angular momentum of the tail keeps it always pointing away from

     the Sun.

D) Gases from the comet, heated by the Sun, push the tail away from the Sun.

E) It is allergic to sunlight.

15)  What is Charon?

A) Pluto's moon

B) the largest known asteroid

C) the largest known comet

D) one of the Galilean moons of Jupiter

E) a moon of Neptune

16)  What drives the motion of the continental plates on Earth?

A) convection cells in the mantle

B) lava flows in trenches along the sea floor

C) the Coriolis force

D) the Earth's magnetic field

E) tidal forces

17)  Why does the burning of fossil fuels increase the greenhouse effect on Earth?

A) Burning fuel warms the planet.

B) Burning releases carbon dioxide into the atmosphere.

C) Burning depletes the amount of ozone, thereby warming the planet.

D) Burning produces infrared light, which is then trapped by existing greenhouse gases.

E) All of the above are true.

18)  What two forces are balanced in what we call gravitational equilibrium?

A) the electromagnetic force and gravity

B) outward pressure and the strong force

C) outward pressure and gravity

D) the strong force and gravity

E) the strong force and kinetic energy

19)  From the center outward, which of the following lists the "layers" of the Sun in the correct

       order?

A) core, radiation zone, convection zone, corona, chromosphere, photosphere

B) core, corona, radiation zone, convection zone, photosphere, chromosphere

C) core, radiation zone, convection zone, photosphere, chromosphere, corona

D) core, convection zone, radiation zone, corona, chromosphere, photosphere

E) core, convection zone, radiation zone, photosphere, chromosphere, corona

20)  What happens to energy in the convection zone of the Sun?

A) Energy slowly leaks outward through the diffusion of photons that repeatedly bounce off

     ions and electrons.

B) Energy is produced in the convection zone by nuclear fusion.

C) Energy is transported outward by the rising of hot plasma and the sinking of cooler plasma.

D) Energy is consumed in the convection zone by the creation of electrons and positrons.

21)  Which of the following statements about the sunspot cycle is not true?

A) The number of sunspots peaks approximately every 11 years.

B) With each subsequent peak in the number of sunspots, the magnetic polarity of the Sun is the

     reverse of the previous peak.

C) The rate of nuclear fusion in the Sun peaks about every 11 years.

D) The cycle is truly a cycle of magnetic activity, and variations in the number of sunspots are

      only one manifestation of the cycle.

E) The number of solar flares peaks about every 11 years.

22)  Why do sunspots appear dark in pictures of the Sun?

A) They are too cold to emit any visible light.

B) They actually are fairly bright but appear dark against the even brighter background of the

     surrounding Sun.

C) They are holes in the solar surface through which we can see to deeper, darker layers of the

     Sun.

D) They are tiny black holes, absorbing all light that hits them.

E) They emit light in other wavelengths that we can't see.

23)  Hydrogen fusion in the Sun requires a temperature (in Kelvin) of

A) thousands of degrees.

B) millions of degrees.

C) billions of degrees.

D) trillions of degrees.

E) any temperature, as long as gravity is strong enough.

24)  If the distance between us and a star is doubled, with everything else remaining the same,

       the luminosity

A) is decreased by a factor of four, and the apparent brightness is decreased by a factor of four.

B) is decreased by a factor of two, and the apparent brightness is decreased by a factor of two.

C) remains the same, but the apparent brightness is decreased by a factor of two.

D) the luminosity remains the same, but the apparent brightness is decreased by a factor of four.

E) is decreased by a factor of four, but the apparent brightness remains the same.

25)  Which of the following terms is given to a pair of stars that appear to change positions in

       the sky, indicating that they are orbiting one another?

A) visual binary

B) eclipsing binary

C) spectroscopic binary

D) double star

E) none of the above

26)  On a Hertzsprung\'2DRussell diagram, where would we find stars that are cool and

       luminous?

A) upper right B)  lower right C)  upper left D)  lower left

1)  Answer:  A

2)  Answer:  A

3)  Answer:  D

4)  Answer:  D

5)  Answer:  A

6)  Answer:  B

7)  Answer:  A

8)  Answer:  C

9)  Answer:  D

10)  Answer:  B

11)  Answer:  E

12)  Answer:  A

13)  Answer:  D

14)  Answer:  A

15)  Answer:  A

16)  Answer:  A

17)  Answer:  B

18)  Answer:  C

19)  Answer:  C

20)  Answer:  C

21)  Answer:  C

22)  Answer:  B

23)  Answer:  B

24)  Answer:  D

25)  Answer:  A

26)  Answer:  A