rest of questions
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Transcript of rest of questions
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Question 13 out of 3 points
What do asteroids and comets have in common?Answer
Selected Answer: Most are unchanged since their formation in the solar
nebula.
Correct Answer: Most are unchanged since their formation in the solar
nebula.
Response Feedback:
Correct, both are left over from the formation of the Solar System
Question 20 out of 3 points
A constellation isAnswer
Selected Answer:
d.
members of a single star cluster
Correct Answer:
c.
stars at varying distances in the same part of the sky
Response Feedback:
Incorrect, the stars in a constellation are not necessarily members of a single star cluster. stars in a single cluster are approximately the same age and distance.
Constellations are just pretty pictures in the sky created by our ancestors to tell stories.
Question 30 out of 3 points
We currently know of approximately how many exo-planets?Answer
Selected Answer: 900
0
Correct Answer: 900
Response Feedback:
Incorrect, see the exo-planets encyclopedia for the latest numbers
Question 43 out of 3 points
A G2V star and a K2V star have the same:Answer
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Selected Answer: none of the
above
Correct Answer: none of the
above
Response Feedback:
Correct, remember for main sequence stars the mass, radius, luminosity and temperature are all related (and all are lower as you get to later spectral types).
Question 50 out of 3 points
Why does the fusion of hydrogen release energy to power the Sun and stars?Answer
Selected Answer:
c.
fusion breaks up hydrogen molecules, releasing energy.
Correct Answer:
b.
fusion combines 4 hydrogen atoms into one helium which has less mass than 4 protons
Response Feedback:
Incorrect, this mass difference powers the stars, think Einstein's equation E = m c2, the energy released is proportional to the mass difference.
If helium was more massive than the 4 hydrogen atoms the stars would not shine.
Question 60 out of 3 points
You observe a star cluster with a main-sequence turn-off point at spectral type G2 (the same spectral type as the Sun). What is the age of this star cluster?Answer
Selected Answer: 4.6 billion years.
Correct Answer: 10 billion years.
Response Feedback:
Incorrect, stars like the Sun live 10 billion years
Question 73 out of 3 points
Which of the following is not a characteristic of the inner planets?Answer
Selected Answer:
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They all have substantial atmospheres.
Correct Answer: They all have substantial
atmospheres.
Response Feedback:
Correct, only Venus and Earth have significant atmospheres
Question 80 out of 3 points
Remembering that the surface temperature of the Sun is ~6000K, a red giant would have a temperature of:Answer
Selected Answer: 30,000
K
Correct Answer: 3000 K
Response Feedback:
Incorrect, a red giant like Arcturus is ~1/2 the (surface) temperature of the Sun.
A 30,000 K star is an O star like Rigel and the Earth is ~300 K.
Question 93 out of 3 points
A star like the Sun will:Answer
Selected Answer:
a.
become a white dwarf
Correct Answer:
a.
become a white dwarf
Response Feedback:
Correct, after it uses all of its hydrogen fuel a star like the Sun will expand into a red giant, then eventually after running out of its core helium become a planetary nebula and then a white dwarf
Question 103 out of 3 points
What was the material out of which the Solar System formed primarily made of?Answer
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Selected Answer: Mostly hydrogen and helium with a small amount
of dust grains
Correct Answer: Mostly hydrogen and helium with a small amount
of dust grains
Response Feedback:
Correct, the Universe is still mostly hydrogen and helium (from the Big Bang)
Question 113 out of 3 points
Your mass would be approximately ( ) times larger than it is here on Earth if you were on a 1 Solar mass white dwarf:Answer
Selected Answer: the
same
Correct Answer: the
same
Response Feedback:
Correct, your mass is always the same. Note that the weight increases as the gravitational force increases.
Question 123 out of 3 points
If the Sun were to suddenly expand to be 10 times its current size of ~0.0047 AU but keep the same mass, the Earth would:Answer
Selected Answer: stay in the same
orbit
Correct Answer: stay in the same
orbit
Response Feedback:
Correct, the force on the Earth would be unchanged since the mass of the Sun is unchanged, so the orbit would not change.
Note this would not be true if the Sun were to expand to be larger than the Earth's orbit of course.
Also note that orbital distances are defined from both object's centers, so while the Earth in some sense is
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"closer" to the Sun's surface, its distance from the Sun's center and hence its orbital distance is unchanged.
Question 133 out of 3 points
Consider two stars, A and B, with the following apparent and absolute magnitudes:
m(A) = -2 (apparent magnitude)M(A) = 10 (absolute magnitude)
m(B) = 3 (apparent magnitude)M(B) = 5 (absolute magnitude)
which is more luminous?
Answer
Selected Answer:
a.
A appears brighter, but B is actually brighter
Correct Answer:
a.
A appears brighter, but B is actually brighter
Response Feedback:
Correct, A's apparent magnitude of -2 (a smaller number) means it appears brighter but B's absolute magnitude of 5 (versus 10 for A) means it is in intrinsically brighter.
Question 140 out of 3 points
When we see a region of a planet that is not as heavily cratered as other regions, we conclude thatAnswer
Selected Answer: the planet formed after the age of bombardment and missed out on getting hit by leftover
planetesimals.
Correct Answer: the surface in the region is younger than the surface in more heavily cratered regions.
Response Feedback:
Incorrect, the regions that have been reformed via vulcanism, erosion, etc most recently have fewer craters
Question 150 out of 3 points
Incandescent light bulbs have a temperature of ~2700 K, this means that their light is emitted mostly:Answer
Selected
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Answer: at optical wavelengths
Correct Answer: at infrared
wavelengths
Response Feedback:
Incorrect, the cooler temperature (relative to the Sun) means that these bulbs emit most of their light at longer - infrared - wavelengths. This is why they are so inefficient.
Question 163 out of 3 points
If we see a high mass Ostar in the Andromeda galaxy tonight, we know that:Answer
Selected Answer: it will have already gone (Type II)
supernova
Correct Answer: it will have already gone (Type II)
supernova
Response Feedback:
Correct, remember that an O star has lifetime of order 1 million years, and so even before the light from an O star reaches us from Andromeda (2 million light years away) the star has been born, evolved, and exploded as a Type II SN before any being in the MIlky Way can see it.
Question 170 out of 3 points
What happens to the core of a star after it ejects a planetary nebula?Answer
Selected Answer: It becomes a neutron
star.
Correct Answer: It becomes a white
dwarf.
Response Feedback:
Incorrect, this is the path stars like the Sun take in becoming white dwarfs
Question 180 out of 3 points
Open clusters contain approximately ( ) stars:Answer
Selected
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Answer: 1,000,000,000
Correct Answer: 1,000
Response Feedback:
Incorrect, open clusters typically contain fewer stars (1,000) than the globular clusters (~100,000-1,000,000) which formed early in the galaxies history.
Question 193 out of 3 points
About how old is the Solar System?Answer
Selected Answer: 5 billion
years
Correct Answer: 5 billion
years
Question 203 out of 3 points
Approximately how many Earth's fit inside the Sun:Answer
Selected Answer:
c.
1,000,000
Correct Answer:
c.
1,000,000
Response Feedback:
Correct, the volume of the Sun is ~1,000,000 times that of the Earth.
Question 213 out of 3 points
The MK-spectral types OBAFGKM must represent a sequence of:Answer
Selected Answer: decreasing
temperatures
Correct Answer: decreasing
temperatures
Response Correct, the first letter of the spectral type is related to the
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Feedback:
effective surface temperature of the star. Not that (for example) M stars can have a variety of radii and hence luminosities (as L=T4R2), and that a supergiant has a larger mass than a giant or main sequence M star.
Question 220 out of 3 points
The Sun will most likely never become a nova or type Ia supernova because such events only happen to stars thatAnswer
Selected Answer: are much more massive than
the Sun
Correct Answer: are in close binary systems
Response Feedback:
Incorrect, novae and type Ia supernovae occur in binary systems where one member is a white dwarf.
Remember that high mass stars become type II supernovae.
Question 230 out of 3 points
On a Hertzsprung-Russell diagram, where on the main sequence would you find stars that have the greatest mass?Answer
Selected Answer: lower
right
Correct Answer: upper left
Response Feedback:
Incorrect, O stars have the largest mass
Question 243 out of 3 points
A main sequence star's luminosity comes from:Answer
Selected Answer:
a.
fusion of hydrogen into helium in the core
Correct Answer:
a.
fusion of hydrogen into helium in the core
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Response Feedback:
Correct, the main sequence is when a star uses nuclear fusion reactions to convert hydrogen into helium in the core of the star.
Question 253 out of 3 points
Type II supernovae occur in evolved O and B stars because they:Answer
Selected Answer: can fuse elements heavier than helium and thus have
large iron cores
Correct Answer: can fuse elements heavier than helium and thus have
large iron cores
Response Feedback:
Correct, remember that iron has the highest binding energy of all elements and so a star cannot extract energy from fusing iron into heavier elements.
Question 263 out of 3 points
Compared to stars like the Sun, B stars like RigeL have:Answer
Selected Answer: lifetimes much shorter than
the Sun
Correct Answer: lifetimes much shorter than
the Sun
Response Feedback:
Correct, hot, luminous massive stars like Rigel burn through there fuel much more quickly and thus have lifetimes much shorter than the Sun.
Question 270 out of 3 points
How thick are Saturn's rings from top to bottom?Answer
Selected Answer: a few kilometers
Correct Answer: a few million
kilometers
Response Feedback:
Incorrect, the rings are incredibly thin
Question 28
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3 out of 3 points
After the collapse began were all parts of the Solar Nebula the same temperature, and if not which part was hottest?Answer
Selected Answer: Not all the same temperature, and the inner parts
were the hottest.
Correct Answer: Not all the same temperature, and the inner parts
were the hottest.
Question 293 out of 3 points
Why do asteroids and comets differ in composition?Answer
Selected Answer: Asteroids formed inside the frost line, while comets formed
outside.
Correct Answer: Asteroids formed inside the frost line, while comets formed
outside.
Response Feedback:
Correct, asteroids formed where the pre-Solar nebula was too hot for ices to form
Question 303 out of 3 points
Type-II supernovae occur when:Answer
Selected Answer:
d.
a massive star collapses after running out of fuel
Correct Answer:
d.
a massive star collapses after running out of fuel
Response Feedback:
Correct, a Type II supernova is when the core of a massive star collapses, releasing energy that explodes the rest of the star
Question 313 out of 3 points
The core of the Sun isAnswer
Selected Answer: much hotter and much denser than its
surface.
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Correct Answer: much hotter and much denser than its
surface.
Response Feedback:
Correct, remember our discussion based upon the average density and the luminosity relationship with temperature and radius
Question 323 out of 3 points
You observe two stars over the course of a year (or more) and find that both stars have measurable parallax angles. Star X has a parallax angle of 1 arc-second. Star Y has a parallax angle of 1/4 of an arc-second. How do the distances to the two stars compare?Answer
Selected Answer: star Y is 4 times further
away
Correct Answer: star Y is 4 times further
away
Response Feedback:
Correct, the parallax angle is equal to (distance)-1, so the more distant star has a smaller parallax, and if the parallax is 4 times smaller then it is 4 times further away.
Question 333 out of 3 points
Hydrostatic equilibrium means that:Answer
Selected Answer: stars have a higher temperature and pressure in their
centers to support the mass of their outer layers
Correct Answer: stars have a higher temperature and pressure in their
centers to support the mass of their outer layers
Response Feedback:
Correct, the concept of hydrostatic equilibrium implies that a star must have a higher pressure in its center to support the weight of the outer layers.
Question 340 out of 3 points
An M-star which is 1/1000th the luminosity of the Sun an 1/10th its mass should live approximatelyAnswer
Selected Answer:
b.
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1 billion years
Correct Answer:
d.
1 trillion years
Response Feedback:
Incorrect, since the amount of energy it puts out is 1/1000th that of the Sun but it has only 1/10th the fuel, it should last 100 times longer- since the Sun lives 10 billion years an M star should live 1 trillion years.
Question 350 out of 3 points
On a Hertzsprung-Russell diagram, where would you find red giant stars?Answer
Selected Answer: lower
right
Correct Answer: upper
right
Response Feedback:
Incorrect, red giants are cool (to the right) and bright (toward the top)
Question 360 out of 3 points
Remembering that the Sun has a surface temperature of approximately 5,800 K, a main sequence A star like Vega will have a temperature of approximately:Answer
Selected Answer: 5,800
K
Correct Answer: 10,00
0K
Response Feedback:
Incorrect, an A star is slightly hotter than the Sun, a star at ~50,000K is an O star (the hottest stars) and all of the other choices are as cool or cooler than the Sun so would not fit an A star.
Question 370 out of 3 points
Imagine a star which has the same luminosity as the Sun but which has a surface temperature that is twice that of the Sun. You would
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then expect that a planet identical to Earth orbiting at 1 AU from this star would:Answer
Selected Answer: be ~4x hotter than the Earth
Correct Answer: be approximately the same temperature
as the Earth
Question 380 out of 3 points
Pluto is now classified as a dwarf planet because:Answer
Selected Answer: its moon Charon is too massive, so the center of mass of
the system is outside Pluto
Correct Answer: it is in the Kuiper belt
Response Feedback:
Incorrect, Pluto has not "cleared" its orbit. Note that it croses Neptune's orbit not that of Uranus.
Question 390 out of 3 points
We can determine the age of a globular cluster by:Answer
Selected Answer: counting the number of neutron stars in the cluster.
Correct Answer: finding the spectral types of the most luminous main
sequence stars.
Response Feedback:
Incorrect, the most massive/luminous main sequence stars left are the ones whose lifetime is less than the age of the cluster, so the cluster must be just older than that age.
All of the stars with lifetimes less than the age of the cluster will have evolved off the main sequence already.
Question 403 out of 3 points
How do the planets near the Sun differ from those farther out?Answer
Selected Answer: The ones nearest the Sun are
generally smallest.
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Correct Answer: The ones nearest the Sun are
generally smallest.
Question 60 out of 3 points
Type II supernovae occur in evolved O and B stars because they:
Answer
Selected Answer:
form white dwarf stars in binary systems
Correct Answer:
can fuse elements heavier than helium and thus have large iron cores
Response Feedback:
Incorrect, remember that iron has the highest binding energy of all elements and so a star cannot extract energy from fusing iron into heavier elements.
Question 110 out of 3 points
About how old is the Solar System?
Answer
Selected Answer:
5 trillion years
Correct Answer:
5 billion years
Question 130 out of 3 points
How thick are Saturn's rings from top to bottom?
Answer
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Selected Answer:
a few hundred kilometers
Correct Answer:
a few million kilometers
Response Feedback:
Incorrect, the rings are incredibly thin