Choose only one answer for each question.
1. We observe a binary system consisting of two stars, Stars A and B.
Star A is a Main Sequence star with 3 solar masses, and Star B has evolved
slightly off the Main Sequence and has 1.5 solar masses. What can we
conclude?
a. Star A started to evolve off the Main Sequence, but then Star B
swept up its red giant envelope and made it go back to the Main Sequence
b. Star B is a Cepheid that is currently in its low-mass phase
c. Star B was originally more massive than Star A, then when it became a
red giant, some of its mass transferred to Star A
d. Stars A and B were originally one star, which split when it became a
red giant.
2. What is the difference between a type I and a type II supernova?
a. a type I supernova happens to a more massive star than a type II
b. a type I supernova happens to a massive star, a type II to a white dwarf
c. a type I supernova happens to a white dwarf, a type II to a massive star
d. the remnant of a type I supernova is a pulsar, and the remnant of
a type II supernova is a white dwarf
3. A type I supernova can be up to ____________ times as luminous as
the sun (i.e. as luminous as ___________ suns)
a. a few thousand (104)
b. a million (106)
c. a billion (109)
d. a trillion (1012)
4. What is required for a white dwarf supernova to occur?
a. the white dwarf must have a binary companion with more than 10 solar
masses
b. the white dwarf must have a Main Sequence binary companion
c. the white dwarf must be gaining mass from its binary companion
d. the white dwarf must lose all of its remnant heat
5. What powers a massive-star supernova?
a. gravitational potential energy from core collapse
b. fusion of iron into gold
c. neutrino emission
d. nuclear fission of massive elements
6. What percentage of the energy emitted by a massive-star supernova is
in neutrinos?
a. 1%
b. 10%
c. 50%
d. 99%
7. About how often do supernovae happen in our galaxy?
a. one every few centuries
b. 1 to 3 per century
c. 150 per century
d. 150 per year
8. What is a likely explanation for why we don't see as many supernovae
in our galaxy as our models predict?
a. Many supernovae are obscured by dust, so their light never reaches us
b. They occur on the other side of the galaxy, too far away to be observed.
c. Supernovae are so short that if we aren't looking directly where the
star exploded when it happens, we would miss it.
d. Like a pulsar, a supernova emits a beam of radiation. Because the
beam is small, the chances of our seeing a given supernova are small.
9. Heavy elements such as gold, mercury, bismuth, and uranium were
formed during
a. the Big Bang
b. Fusion in super-massive stars
c. S process in novae
d. R and S process in supernovae
10. Why can't steady core or shell fusion in a star create elements more
massive than iron?
a. only a star more massive than 100 solar masses could do this, and such
stars are unstable
b. the high temperatures in stellar interiors destroy more massive nuclei
c. nuclei heavier than iron are radioactive and fall apart quickly
d. making nuclei heavier than iron by fusion requires energy, instead of
generating energy like the fusion of light elements
11. What is the difference between the R and S processes?
a. the R process adds protons to nuclei, the S process adds neutrons
b. the R process happens in red giants, the S process in supernovae
c. the R process happens in type I supernovae, the S process in type II
d. the R process adds neutrons rapidly, the S process adds them slowly
12. After all its fuel has been exhausted, the sun will end up as:
a. a white dwarf with a mass less than 1 solar mass
b. a nova, with a 1 solar mass white dwarf as the remnant
c. a supernova, with a neutron star remnant
d. a black hole
13. What happens when the mass of a white dwarf exceeds the Chandrasekhar
limit?
a. it begins steady carbon fusion in its core
b. it collapses into a black hole
c. it goes supernova
d. it becomes a Cepheid
14. What is a pulsar?
a. a variable star whose period and luminosity are related
b. a burst of gamma rays from a neutron star
c. the rapidly-spinning neutron core left over after a supernova
d. a signal from extraterrestrial intelligent life
15. Neutron stars can spin:
a. up to about 1/2 the frequency of the sun, about once every 50 days
b. up to the frequency of the sun, about once every 20 days
c. up to 15,000 times the frequency of the sun, about once a minute
d. up to a billion times the frequency of the sun, about once a millisecond
(10-3 second)
16. A black hole is
a) An object so massive that light can not escape from its surface
b) An object so small that light can not escape from its surface
c) An object whose escape velocity exceeds the speed of light
d) Any massive celestial object that does not emit light
17. If the period of a Cepheid is measured, its ____________ can be
determined, from which its ____________ can be calculated.
a. color; age
b. luminosity; distance
c. brightness; mass
d. spectral type; radius
18. Drs. Harden, Petrie, and Rozyczka have found a lone star about 300 light
years away from us, with a mass of about 5 solar masses. They claim to have
discovered a white dwarf. Would you support their discovery?
a) Yes, it sounds perfectly reasonable.
b) No, a 5 solar mass object cannot be a white dwarf
c) No, a white dwarf 300 light years away would be much too faint (and
not visible in the optical anyway) to be seen
d) No, white dwarfs are only found in binary star systems.
19. After additional observations made with an optical telescope,
they recalculate the mass and distance to obtain 2.5 solar masses and 3000
light years. They conclude that it is a neutron star. Would you support
this conclusion?
a) Yes, it sounds perfectly reasonable.
b) No, a 2.5 solar mass object can not be a neutron star
c) No, a neutron star 3000 light years away would be much too faint to be
seen
d) No, neutron stars are only found in binary star systems.
20. After having observed this mystery star for a month, they find that the
first estimate of mass (5 solar masses) and the second estimate of distance
(3000 light years) are correct. They also find that the star's brightness
varies regularly, brightening for a few days, then fading back to its
original brightness. What must this star be?
a) A nova
b) A supernova type I
c) A supernova type II
d) A Cepheid variable