REVIEW: Astronomy 106 Test 5

Multiple Choice

Identify the letter of the choice that best completes the statement or answers the question.

____ 1. Why do main sequence stars have different surface temeperatures?

a.	Their chemical compositions differ. Hot stars have more hydrogen than cool stars
b.	They have different masses - hot stars are more massive than cool stars
c.	They have different masses - cool stars are more massive than hot stars
d.	neutrino production is different in stars with different temperatures
e.	It depends on their age - new stars are cooler because the thermonuclear reaction is just starting

____ 2. In what region of the galaxy do new stars form?

a.	in the halo
b.	in globular star clusters
c.	the the galactic disk
d.	near the center of the galaxy
e.	in the corona

____ 3. Why are most stars found on the main sequence?

a.	main sequence stars are cooler than stars off the main sequence.
b.	main sequence stars are more plentiful at this stage of cosmic evolution
c.	other evolutionary stages - protostar and giant - are very short compared to the main sequence.
d.	main sequence stars are much brighter than stars off the main sequence and are, therefore, easier to see
e.	most main sequence stars are in hydrostatic equilibrium

____ 4. From what type of objects do stars form?

a.	giant molecular clouds
b.	Extremely hot gases ejected from supernovae
c.	cometary materials from interstellar space
d.	planetary collisions
e.	intergalactic shock waves

____ 5. What is nucleosynthesis?

a.	energy generation through the breakup of large nuclei
b.	process of turning neutral atoms into ions
c.	the process of exciting nuclei in the ground state so that they are ready to emit radiation
d.	the process of fusing two smaller nuclei together to make larger nuclei
e.	also known as fission

____ 6. In what stage of a star's life does it become a red giant?

a.	in the beginning, at the protostar stage
b.	in the middle, when it is in hydrostatic equilibrium
c.	after its outer shell drifts away as a planetary nebula
d.	right before its surface drops below the event horizon
e.	in the later stages, when it moves off the main sequence.

____ 7. What property of a star determines whether it ultimately becomes a white dwarf, neutron star, or black hole?

a.	its temperature
b.	its location in the galaxy
c.	its diameter
d.	its mass
e.	its chemical composition

____ 8. Who discovered pulsars (rapidly rotating neutron stars) in 1967

a.	Vera Ruben
b.	Jocelyn Bell
c.	Cecilia Payne
d.	Annie Jump Canon
e.	Edwin Hubble

____ 9. What is the Chandrasekhar Limit?

a.	The smallest that a body can be and still ignite thermonuclear fusion
b.	The greatest mass that a white dwarf can have without imploding into a neutron star or black hole
c.	The maximum number of stars that can be seen from the northern hemisphere with the naked eye.
d.	The greatest mass a neutron star can have before it implodes into a black hole
e.	The largest nuclei that can be synthesized in the core of massive stars

____ 10. What prevents a white dwarf from collapsing?

a.	degenerate neutron pressure
b.	hydrostatic equilibrium
c.	degenerate electron pressure
d.	degernerate proton pressure
e.	nucelosynthesis

____ 11. Who discovered the thermonuclear reaction known as the proton-proton chain?

a.	Arthur Eddington
b.	Vera Ruben
c.	Jocelyn Bell
d.	Edwin Hubble
e.	Hans Bethe

____ 12. What is the approximae main sequence lifetime of a star with the mass of the sun?

a.	10,000 years
b.	1,000,000 years
c.	10,000,000,000 years
d.	100,000,000,000 years
e.	1,000,000,000 years

____ 13. What is the nuclear reaction which powers the sun?

a.	fission
b.	fusion
c.	the proton-proton chain
d.	a and b
e.	b and c

____ 14. Why is a temperature of at least ten million degrees requried to ignite a thermonuclear reaction?

a.	to overcome the electromagnatic repulsion between protons
b.	to overcome the electromagnetic repulsion between electrons
c.	to overcome the gravitational repulsion between charges
d.	to slow down the naturtal attraction between protons and electrons
e.	to split larger nuclei into smaller nuclei

____ 15. When light from a star passes close to the sun, the position of that star on the celestial sphere appears

a.	to be further from the sun than when the sun is not present
b.	to be closer to the sun than when the sun is not present
c.	to disappear
d.	to be in the same place as it is when the sun is not present
e.	to be closer or further from the sun, depending on the spectral class of the star

____ 16. Einstein's ___________ principle states that an observer cannot distinguish between the force exerted on her due to an acceleration and force exerted on her by a massive body

a.	uniformity
b.	relativity
c.	cosmological
d.	plenitude
e.	equivalence

____ 17. According to general relativity, what is gravity?

a.	a force field
b.	a curvature of space-time
c.	equivalent to dark matter
d.	the same as energy
e.	depends on the frame of reference

____ 18. What happens to time in a gavitational field?

a.	Time flows at the same rate in all graviational fields
b.	Time speeds up in a gravitational field. The stronger the field, the faster time flows
c.	Time slows down in a gravitational field. The stronger the field, the slower time flows.
d.	The stronger the gravitational field, the more difficult it is to measure time
e.	none of the above

____ 19. Why are astronauts orbiting the Earth weightless?

a.	They are beyond the reach of Earth's gravitational field
b.	The gravitational fields of Earth, the moon and the sun pull in equal and opposite directions and cancel each other out.
c.	The acceleration of the spacecraft produces a force that is equal and opposite to the Earth's gravitational field.
d.	The astronauts are following the curvature of space around a massive body (the Earth)
e.	They are weightless relative to the spacecraft but not relative to the Earth

____ 20. What was the first test of general relativity that was widely viewed as confirming the theory?

a.	The precise measurement of the speed of light in 1919
b.	The detonation of the first atomic bomb in 1945
c.	The determination that time runs slower in a gravitational field by comparing the elapsed time recorded by two synchronized clocks, one on the ground floor, and one on the fifth floor.
d.	The discovery of intese radiation from a black hole
e.	The distortion of the star pattern around the sun during an eclipse in 1919

____ 21.

The above drawing shows the positions of 5 stars on the celestial sphere when the sun is passing through. If the sun were not there

a.	the stars would be farther apart
b.	the stars would be closer together
c.	the position of the stars would be exactly the same
d.	some stars would be closer together, some farther apart, and some would be in the same place
e.	their positions would be different, but it would depend on their spectral classifications

____ 22. What does the equation E=mc² mean?

a.	the speed of light is always the same
b.	a gravitational field cannot be distinguished from an acceleration
c.	energy and mass are the same thing
d.	time slows down in a gravitational field
e.	mass increases as its velocity increases

____ 23. Which of the following would feel no gravitational force?

a.	An astronaut in a spaceship orbiting Jupiter
b.	An astronaut in a spaceship drifting in interstellar space
c.	An astronaut in a spaceship accelerating in interstellar space
d.	All of the above
e.	Only A and B

____ 24. Arrange the three stellar remnants in according to their diameters, largest to smallest

a.	black hole, neutron star, white dwarf
b.	white dwarf, neutron star, black hole
c.	neutron star, black hole, white dwarf
d.	white dwarf, black hole, neutron star
e.	black hole, white dwarf, neutron star

____ 25. Where are nuclei larger than iron (Fe) synthesized?

a.	In the cores of stars 8 tmes the mass of the sun or more
b.	In the cores of stars between 8 and 25 times the mass of the sun
c.	In the cores of stars 8 times the mass of the sun or less
d.	In supernovae explosions
e.	In the cores of stars at least 20 times the mass of the sun

____ 26. The event horizon is

a.	equal to the diameter of a star whose escape velocity just exceeds the speed of light
b.	the initation of thermonuclear fusion in the cores of large stars
c.	the point at which a star exhusts its nuclear fuel
d.	the point at which a white dwarf becomes a neutron star
e.	the moment at which a supernova explodes

____ 27. A star with a mass 10 times that of the sun will finish its life cycle as

a.	a white dwarf from its core and a planetary nebula
b.	a black hole from its core and a planetary nebula
c.	a neutron star from its core and and widely scattered debris from the supernova
d.	a black hole from its core and widely scatterd debris from the supernova
e.	a neutron star from its core and a planetary nebula

____ 28. A star with a mass 5 times that of the sun will finish its life cycle as

a.	a white dwarf from its core and a planetary nebula
b.	a black hole from its core and a planetary nebula
c.	a neutron star from its core and and widely scattered debris from the supernova
d.	a black hole from its core and widely scatterd debris from the supernova
e.	a neutron star from its core and a planetary nebula

____ 29. A star with a mass 26 times that of the sun will finish its life cycle as

a.	a white dwarf from its core and a planetary nebula
b.	a black hole from its core and a planetary nebula
c.	a neutron star from its core and and widely scattered debris from the supernova
d.	a black hole from its core and widely scatterd debris from the supernova
e.	a neutron star from its core and a planetary nebula

____ 30. An astronaut on a spaceship traveling at 90% the speed of light is headed for a planet circling the star Sirius. The time required to reach Sirius

a.	will be shorter for the astronaut than for an observer on the Earth monitoring the flight .
b.	will be longer for the astronaut than for an observer on the Earth monitoring the flight .
c.	will be the same for the astronaut as for an observer on the Earth monitoring the flight.
d.	will depend on the technique used to make the measurement.
e.	will appear to be shorter for the astronaut, but will actually be the same as for an observer on the Earth monitoring the flight .