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ORM 3 (Special Code P = 3) Astronomy 101-0 Exam #2 Winter 2018 Prof. Smutko The speed of light in a vacuum: c = 300,000 km/sec = 186,000 miles/sec 1)
Homogeneous means: A.
the same in all directions D. the Universe is expanding B.
the same at all places E. our universe is one of many other universes C.
the Universe was created so that intelligent life could arise 2)
Star Alpha is 8 times farther away from Earth than star Omega. Star Alpha is also 16 times as luminous as star Omega. How does their apparent brightness compare as seen from here on Earth? A.
Alpha is 4 times fainter D. Alpha is 16
4
= 65,536 times brighter B.
Omega is 64 times brighter E. Omega is 8
4
= 4096 times brighter C.
they seem to be the same brightness 3)
If the Universe is really expanding, why aren’t people being stretched apart by the expansion? A.
Trick question: we are
being stretched apart but it is so slow we do not notice it B.
The expansion only affects galaxies that are billions of light years away C.
The chemical bonds that hold a person together are much stronger than the stretching of space D.
Gravity holds people together against the expansion E.
The expansion only affects things made from hydrogen and helium (such as stars) 4)
What is the weak anthropic principle? A.
The laws of physics must be compatible with intelligent life B.
The universe is homogeneous and isotropic C.
The purpose of the universe is to form life D.
The universe has always been basically the same E.
The laws of physics are randomly set within a universe when it forms 5)
What is the common trait of all main-sequence stars? A.
They are in the final stage of their lives. B.
They generate energy through hydrogen fusion in their core. C.
They are all spectral type G. D.
They are all the same color. E.
They all have approximately the same mass. 6)
What happens when a star exhausts its core hydrogen supply? A.
Its core contracts, but its outer layers expand and the star becomes bigger and brighter. B.
Its outer layers contract, and the star becomes smaller and dimmer overall. C.
Its outer layers contract, and the star becomes hotter and brighter overall. D.
Its outer layers expand, becoming bigger but dimmer overall. E.
Its core contracts, but its outer layers expand and the star becomes bigger but cooler and therefore remains at the same brightness. 7)
What is the Chandrasekhar limit? A.
the maximum mass of a white dwarf B.
the maximum mass of a neutron star C.
the minimum mass required for a star to begin fusion in its core D.
the minimum temperature needed to see absorption lines in a star’s spectrum E.
the minimum temperature needed for fusion to occur in the core of a star 8)
Which of the following is closest in mass
to a white dwarf? A.
the Moon D. Mount Everest B.
Earth E. the Sun C.
Jupiter 9)
The idea that the universe had an instant when it began is implied by its A.
infinite size D. isotropy B.
homogeneity E. large “heavy” element content C.
expansion
F
ORM 3 (Special Code P = 3) Astronomy 101-0 Exam #2 Winter 2018 Prof. Smutko The HR Diagram at right is provided to assist with answering questions 10-14. 10)
Which group represents stars of the largest radii? A.
A D. D B.
B E. E C.
F 11)
Which is hotter on the surface, a main sequence star with a luminosity equal to the Sun’s or a white dwarf with a luminosity 100 times smaller than the Sun’s? A.
the main sequence star B.
the white dwarf C.
They have the same temperature. D.
There is insufficient information to determine this. 12)
Which group represents stars with the shortest main-sequence lifetimes? A.
A D. D B.
F E. E C.
C 13)
Which group represents stars that are extremely bright and emit most of their radiation as ultraviolet light? A.
A D. D B.
F E. E C.
C 14)
Which group represents stars that do not
have ongoing nuclear reactions?
A.
A D. D B.
B E. E C.
C 15)
Which statement is the most correct about the comparison between a spectral type G5 main sequence star and a spectral type O5 main sequence star? A.
The G5 star is cooler, less luminous, and will not live as long as the O5 main sequence star. B.
The G5 star is hotter, more luminous, and will live longer than the O5 main sequence star. C.
The G5 star is hotter, more luminous, and will not live as long as the O5 main sequence star. D.
The G5 star is less luminous, cooler, and will live longer than the O5 main sequence star. E.
The G5 star is hotter, less luminous, and will live longer than the O5 main sequence star. 16)
Given that Type Ia supernovae are such good standard candles, why don't we use them to measure the distance to all
galaxies? A.
They are rare events, so we have observed them in only a tiny fraction of all galaxies. B.
We cannot see them beyond a distance of about 100 million light-years. C.
They can occur only in spiral galaxies, not elliptical galaxies. D.
We would, but we don't have enough telescopes. E.
We can only observe Type Ia supernovae nearby in the Milky Way galaxy. 17)
What is a planetary nebula? A.
a disk of gas surrounding a protostar that may form into planets B.
what is left of the planets around a star after a low-mass star has ended its life C.
the expanding shell of gas found around the remnant of a low-mass star D.
the molecular cloud from which new stars form E.
the expanding shell of gas that is left when a white dwarf explodes as a supernova c e Temperature (K) Luminosity (solar units) Spectral Type Absolute magnitude 20,000 10,000 5,000 O5 B5 A5 F5 G5 K5 M5 10,000
1,000 100 10 1 .1 .01
.001 .0001 a b d f -5 0 5 10 15 Main Sequence Red Giants White Dwarfs
F
ORM 3 (Special Code P = 3) Astronomy 101-0 Exam #2 Winter 2018 Prof. Smutko 18)
Why is iron significant to understanding how some supernovae occur? A.
Iron is the heaviest of all atomic nuclei, and thus no heavier elements can be made. B.
Supernovae often leave behind neutron stars, which are made mostly of iron. C.
The fusion of iron into uranium is the reaction that drives a supernova explosion. D.
Iron cannot release energy either by fission or fusion. E.
Iron makes a very strong chemical bond with oxygen that releases large amounts of energy. 19)
The core of the Sun is A.
at the same temperature and density as the surface. B.
at the same temperature but denser than the surface. C.
hotter and denser than the surface. D.
constantly rising to the surface through convection. E.
composed of iron. 20)
What is the minimum initial mass of a star required for nuclear fusion to begin in its core? A.
3 M
☉
D. 0.08 M
☉
B.
1.4 M
☉
E. 0.5 M
☉
C.
0.00001 M
☉
21)
The proton-proton chain (process) is A.
the most important set of nuclear reactions through which the Sun fuses hydrogen into helium. B.
the linkage of numerous protons into long chains. C.
another name for the force that holds protons together in atomic nuclei. D.
an alternative way of generating energy that is different from the fusion of hydrogen into helium. E.
the electrical repulsion of the two positive charges. 22)
A spectral line emitted from a galaxy at 500 nm is observed at what wavelength when its redshift is z=5? A.
505 nm D. 2500 nm B.
495 nm E. 3000 nm C.
100 nm 23)
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.
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. 24)
Suppose that you measure the parallax angle for a particular star to be 0.5 arcseconds. The distance to this star must be A.
0.5 light-year. D. 5 parsecs. B.
0.5 parsec. E. 2 parsecs. C.
5 light-years. 25)
Which of the following people reorganized the spectral classification scheme into the one we use today and personally classified over 400,000 stars? A.
Annie Jump Cannon D. Jocelyn Bell-Burnell B.
Henrietta Leavitt E. Edward Pickering C.
Caroline Herschel 26)
Why are Cepheid variables so important for measuring distances in astronomy? A.
They all have the same luminosity. B.
They all have the same period. C.
Their luminosity can be determined from their period. D.
They are close enough to have a detectable parallax. E.
They are always visible from the Earth’s Northern hemisphere (e.g. Polaris, the North Star).
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F
ORM 3 (Special Code P = 3) Astronomy 101-0 Exam #2 Winter 2018 Prof. Smutko 27)
Ten parsecs (pc) is about A.
150 million kilometers. D. 33 light-years B.
10,000 meters. E. 10 times the distance from the Earth to the Sun. C.
10 parallax seconds of angle. 28)
How was Edwin Hubble able to use his discovery of a Cepheid in Andromeda to prove that “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 a Cepheid in Andromeda, was able to determine the distance to it, and showed that Andromeda was far outside the Milky Way Galaxy. C.
From the period-luminosity relation for Cepheids, he was able to determine the distance to Andromeda and show that Andromeda was far outside the Milky Way Galaxy. D.
Since a Cepheid is a type of luminous galaxy, when he found one in Andromeda he was able to prove that Andromeda was a separate galaxy from the Milky Way. E.
He was lucky enough to observe the Cepheid explode in a Type II supernova. 29)
What do astronomers mean when they say that we are all “star stuff”? A.
that life would be impossible without energy from the Sun B.
that Earth formed at the same time as the Sun C.
that the carbon, oxygen, and many elements essential to life were created by nucleosynthesis in stellar cores D.
that the Sun formed from the interstellar medium: the “stuff” between the stars E.
that the Universe contains billions of stars 30)
What do we mean by the event horizon
of a black hole? A.
It is the very center of the black hole. B.
It is the distance from the black hole at which stable orbits are possible. C.
It is the place where X-rays are emitted from black holes. D.
It is the point beyond which neither light nor anything else can escape. E.
It is the distance from the Earth to the black hole. 31)
Compared to the main sequence star it evolved from, a red giant is A.
hotter and brighter. D. cooler and dimmer. B.
hotter and dimmer. E. the same temperature and brightness. C.
cooler and brighter. 32)
After a Type II supernova event, what is left behind? A.
always a white dwarf D. either a white dwarf or a neutron star B.
always a neutron star E. either a neutron star or a black hole C.
always a black hole 33)
The predictions of special relativity can sound implausible at first. What observational evidence do scientists have that the theory is correct? A.
Subatomic particles in accelerators exhibit effects of time dilation and mass increase at high speeds. B.
Light is always observed to travel at the same speed. C.
Time dilation can be observed in airplanes. D.
All of the above E.
None of the above 34)
What is the basic definition of a black hole
? A.
any compact mass that emits no light B.
a dead star that has faded from view C.
any object from which the escape velocity exceeds the speed of light D.
any object made from dark matter E.
a dead galactic nucleus that can only be viewed in infrared wavelengths
F
ORM 3 (Special Code P = 3) Astronomy 101-0 Exam #2 Winter 2018 Prof. Smutko 35)
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 D. a black hole B.
a white dwarf E. Everything will be basically the same as it is now. C.
a rapidly spinning pulsar 36)
What is a standard candle? A.
an object for which we are likely to know the true luminosity B.
an object for which we can easily measure the apparent brightness C.
all objects found to be at the same distance from the Earth D.
any star for which we know the exact apparent brightness E.
any objects having the same surface temperature 37)
Based on current estimates of the value of Hubble's constant, how old is the universe? A.
between 4 and 6 billion years old D. between 16 and 20 billion years old B.
between 8 and 12 billion years old E. between 20 and 40 billion years old C.
between 12 and 16 billion years old 38)
Why are Type Ia supernovae more useful than Type II supernovae for measuring cosmic distances? A.
Type II supernovae are only found in nearby galaxies, but a Type Ia could be any distance away. B.
Type Ia supernovae are much more common than Type II supernovae. C.
Type Ia supernovae follow a period-luminosity relation, while Type II supernovae do not. D.
Type Ia supernovae all have roughly the same true peak luminosity, while Type II supernovae come in a wide range of peak luminosities. E.
Type II supernovae are too faint to observe in distant galaxies. 39)
In what way do observations of Mercury support Einstein's general theory of relativity? A.
Mercury's orbit slowly changes in a way that matches the prediction of general relativity but disagrees with the prediction based on Newton's universal law of gravitation. B.
Einstein discovered that time runs slower on Mercury than on Earth, as his theory predicted. C.
Einstein was able to explain the fact that Mercury orbits the Sun exactly twice for every three rotations, and Newton's theory of gravity cannot account for this. D.
We can see that Mercury lies deeper in the spacetime “dimple” that surrounds the Sun than does Earth. E.
Mercury’s position in the sky changed during the solar eclipse of 1919, exactly as Einstein predicted. 40)
What two properties of galaxies did Edwin Hubble graph to discover the expansion of the Universe? A.
velocity and distance D. luminosity and temperature B.
luminosity and distance E. age and distance C.
velocity and temperature 41)
If a galaxy is moving away from us at 2500 km/sec, it must be (assuming H
0
= 50 km/s/Mpc) at a distance of A.
1 Mpc. D. 500 Mpc. B.
25 Mpc. E. 2500 Mpc. C.
50 Mpc. 42)
Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together? A.
Nuclei normally repel because they are all positively charged and can be made to stick only when brought close enough for the strong force to take hold. B.
Nuclei are attracted to each other by the electromagnetic force, but this force is only strong enough to make nuclei stick when they are very close together. C.
Nuclei have to be very hot in order to fuse, and the only way to get them hot is to bring them close together. D.
Fusion can proceed only by the proton-proton chain, and therefore requires that protons come close enough together to be linked up into a chain. E.
Gravity is a very weak force, so the nuclei must be very close to each other in order for gravity to fuse them together.
F
ORM 3 (Special Code P = 3) Astronomy 101-0 Exam #2 Winter 2018 Prof. Smutko 43)
The most distant stars we can currently measure distances to using stellar parallax are approximately A.
8 parsecs away. D. halfway across the Milky Way Galaxy. B.
500 parsecs away. E. in the Andromeda Galaxy. C.
36 light years away. 44)
What kind of star is most likely to become a Type Ia supernova? A.
a B star D. a white dwarf star with a red giant binary companion B.
a star like our Sun E. a pulsar C.
two O stars in orbit around each other 45)
Will our Sun contribute “heavy” elements (i.e. with high atomic numbers) to the cosmos at the end of its life? A.
Yes, all stars do. B.
No, only high mass stars make heavy elements, and our Sun is a low mass star. C.
It is possible, but there is no way for us to know for certain. D.
Yes, but only because it is a low mass star and has plenty of time to produce those heavy elements. E.
No, when the Sun explodes as a supernova, all of its elements will be converted into hydrogen again.
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