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astro 3

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The temperature of the photosphere of the Sun is closest to:
6000 K
Which of the following could have been habitable if the Sun had been twice as massive?
Jupiter's moons
Which is NOT true?
A. A star that appears brighter than another is always closer.
B. A blue Main Sequence star has a higher luminosity than a red main sequence star
C. More massive Main Sequence stars are always both hotter and brighter than less massive Main Sequence stars
D. A B-type Main Sequence star that appears 100 times brighter than another B type Main Sequence star is 10 times closer
E. The spectrum of a star allows us to estimate its temperature
A. A star that appears brighter than another is always closer.
How do astronomers measure the temperature of stars?
By looking at which absorption lines are present in the star's spectrum.
A 2 solar mass main sequence star is at the same distance as a 0.2 solar mass main sequence star. Which star appears
brighter?
The 2 solar mass main sequence star
About how many stars does a globular cluster have?
Tens to hundreds of thousands
One star is three times further away than another. The parallax angle of the more distant star is:
three times smaller than that of the nearer star
When using different points in the Earth's orbit as a baseline
for a parallax experiment it is best to do the observations:
6 months apart.
When a star is burning Helium in its core and has puffed out its outer layers, it is:
a red giant
A star that is 70 percent the mass of our Sun would have a habitable zone that:
includes Venus but not the Earth
The largest fraction of nearby stars (e.g. within 100 light years) are:
red dwarfs
A 3 solar mass main sequence star is at the same distance as a 0.4 solar mass main sequence star. Which star appears
brighter?
the 3 solar mass main sequence star
Where are the globular clusters found?
In the halo, spherically distributed around the Milky Way center
Why would a person be torn apart as he fell feet first into a black hole?
because the force on his feet would be much greater than the force on his head.
Put one of your thumbs at arm's length in front of your face. Now focus on something in the background and look through one eye at a time.

What do you notice about your thumb?
It appears to move more when it's closer.
In order that nuclear reactions will begin in the core of a protostar it must become
hot and dense
A large patch of darkness surrounded by many stars is probably a:
Bok Globule
How did Harlow Shapley determine the distances to globular clusters in the Milky Way galaxy?
He used the Period-Luminosity Relation of RR Lyrae variable stars so they could be used as standard candles.
Which is the most massive star?
A. Star of 0.5 solar masses
B. Coolest possible main sequence star
C. Type B main sequence star
D. Type G main sequence star
E. Hottest possible main sequence star
Hottest possible main sequence star
How do small stars die? About how large are their remnants?
They become white dwarfs, about the size of the Earth.
The brightest 100 stars viewed from Earth are mostly not on the main sequence (even though most stars are) because:
the most luminous stars are giants and supergiants that have already finished their main sequence lifetimes.
What kinds of objects are found in the Milky Way disk?
A. Blue stars
B. Some red stars
C. Open clusters
D. Gas and dust
E. All of the above
All of the above
What happens when you drop a clock into a black hole?
The clock appears to be advancing slowly from the point of view of an outside observer, but normally for an observer falling with the clock.
What doesn't a main sequence star collapse under its own gravity?
the outward force of gas pressure from its interior
Which type of binary gives information about the star sizes in addition to the combined masses?
eclipsing binary
Which star is the closest if all have the same apparent brightness?
A. a temperature 6000 K main sequence star
B. a red giant
C. a temperature 10000 K main sequence star
D. a main sequence star with a luminosity 100 times that of the Sun
E. white dwarf
white dwarf
If two stars are the same temperature, how can one be more luminous than the other?
It can have a larger radius.
What is the closest stellar system to the Solar System & how far away is it?
Alpha Centauri, about 4.3 light years away
Why are novae much more common than supernovae?
A white dwarf's mass slowly decreases with each nova but the whole white dwarf is completely obliterated during a supernova
An "onion skin" shell burning structure develops in:
a star much more massive than the Sun.
31. Which of the following is FALSE?
A. Stars condense within Bok globules.
B. A supernova explosion occurs just before a massive star forms.
C. A brown dwarf is a case where the temperature of a protostar did not grow enough to burn Hydrogen.
D. The Eagle nebula is an example of a giant molecular cloud.
E. A classical T-Tauri star forms with a disk around it.
B. A supernova explosion occurs just before a massive star forms.
What fraction of the visible matter in the Milky Way Galaxy disk is in the form of gas and dust (and not stars)?
10 percent
What is the Trapezium?
A. Four massive stars at the heart of the Orion Nebula
B. Three massive stars on the outskirts of the Orion Nebula
C. A few hot stars whose ultraviolet light is affecting the formation of other stars
D. Both A and C
E. Both B and C
Both A and C
A 3 solar mass main sequence star is at a larger distance than a 0.4 solar mass main sequence star. Which star appears brighter?
We cannot tell with the information given.
The upper right corner of the Hertzsprung-Russell diagram has:
the coolest and most luminous stars
Tycho's supernova was of Type Ia. What happened to the companion star when the white dwarf went supernova?
It went zooming away at the velocity it had from its orbit.
The Milky Way galaxy has a rotation curve that:
stays constant out to large radii in the disk, indicating the presence of dark matter.
How much longer does the Sun have to burn hydrogen
to helium at its core?
about 5 billion years
Which is NOT true about neutron stars?
A. They have radii much larger than the Sun.
B. They sometimes are observed as pulsars.
C. They sometimes remain after a supernova.
D. They are rapidly rotating.
E. They have strong magnetic fields.
A. They have radii much larger than the Sun.
What is Deuterium, also known as Hydrogen-2?
one proton and one neutron
What provides the energy (and so light and heat) of a star?
Atomic energy/nuclear reactions
What is the general result of the proton-proton chain?
4 H -> He + energy + other products
Where is the Sun located in the Milky Way?
About 2/3 of the way out in the disk.
If you could convert the entire mass of the Sun (mass 2 x 1033g) into pure energy, how much energy would be produced (in ergs) ? The speed of light c = 3 x 1010cm/s.
1.8 x 1054ergs
Which of the following is the coldest at its surface?
A. white dwarf
B. type K main sequence star
C. main sequence star with a radius ten times the Sun's radius
D. 3 solar luminosity main sequence star
E. blue main sequence star
B. type K main sequence star
Have objects like Jupiter been found? How?
Yes, hot Jupiters have been found from the radial velocity method.
Why does the Sun appear red at sunrise and sunset?
Light passes through more atmosphere and red light gets through, whereas blue light scatters
Which of the following statements is TRUE?
A. The blackbody spectrum peaks at a longer wavelength for a red supergiant than for a blue main sequence star.
B. Helium absorption lines only appear in the coolest main sequence stars.
C. The blackbody spectrum peaks at a shorter wavelength for a red supergiant than for a blue main sequence star.
D. The blackbody spectrum peaks at a longer wavelength for a red supergiant than for a red main sequence star of the same spectral class.
E. The blackbody spectrum peaks at a shorter wavelength for a red supergiant than for a red main sequence star of the same spectral class.
A. The blackbody spectrum peaks at a longer wavelength for a red supergiant than for a blue main sequence star
What is the density at the center of a black hole?
Infinity
Which is the longest time?
A) one hour
B) the time it takes a photon to pass through the corona of the Sun
C) the time it takes a photon to pass from the photosphere of the Sun to the Earth
D) the time it take light to traverse the convective zone of the Sun
E) the time it takes for a photon to pass through the radiative zone of the Sun
E) the time it takes for a photon to pass through the radiative zone of the Sun
What is the brightest star in the nighttime sky?
B) Sirius the Dog Star
Which of the following is TRUE?
A) The Eagle nebula is an example of a planetary nebula.
B) A brown dwarf is a case where the temperature of a protostar did not grow enough to burn Hydrogen.
C) All Messier objects are actually comets.
D) Bok globules are very luminous regions in the interstellar medium.
E) A supernova explosion occurs just before a massive star forms.
B) A brown dwarf is a case where the temperature of a protostar did not grow enough to burn Hydrogen.
The Sun will end its life as a:
white dwarf
A planetary nebula:
is the ejected envelope of a low to intermediate mass star
Consider star C, a measly 3000 K star, and star D, an impressive 9000 K star. Assuming they are about the same size, how do their luminosities compare?
Star D is 81 times as luminous as star C.
A 10 solar mass star:
C) will eventually develop an Iron core
What is Deuterium, also known as Hydrogen-2?
E) one proton and one neutron
What are the young cousins of globular clusters?
C) Open Clusters
The corona of the Sun:
D) is visible during a solar eclipse
One star is four times further away than another. The parallax
angle of the more distant star is:
A) four times larger than that of the nearer star.
B) the same as the nearer star.
C) sixteen times larger than that of the nearer star.
D) sixteen times smaller than that of the nearer star.
E) four times smaller than that of the nearer star.
E) four times smaller than that of the nearer star.
A large luminosity star:
E) emits more light than a low luminosity star
A 2 solar mass main sequence star is at the same distance as a 0.2 solar mass main sequence star. Which star appears
brighter?
A) The stars are approximately the same brightness
B) We cannot tell with the information given
C) The 2 solar mass main sequence star
D) It depends on the phase of the Moon
E) The 0.2 solar mass main sequence star
C) The 2 solar mass main sequence star
What happens when a planet passes in front of its star (i.e. between the star and us)?
E) The star appears to decrease in brightness, and then the star moves toward us
The lower right corner of the Hertzsprung-Russell diagram has:
A) the coolest and least luminous stars
Do you remember how we measure distances to stars?
C) We use parallax
A 16 solar mass main sequence star is at the same distance as a 1 solar mass main sequence star. Which star appears
brighter?
D) the 16 solar mass main sequence star
Fill in the blank in the following chemical reaction that occurs in the Sun: Deuterium+ proton = ?? + energy:
E) helium-3
What is a nova?
E) A white dwarf that periodically blasts layers of gas into space
The stars in the halo of our galaxy are:
D) older and redder than those in the disk.
What is the lowest rung on the astronomical distance ladder?
the Solar system
What is at the very center of the Milky Way and what is the best evidence for it?
C) A supermassive black hole- detections of stellar orbits over 8 years
The heaviest nuclei of all are formed:
B) during a supernova explosion
What kinds of stars are being looked at to find extrasolar planets?
E) Stars with large parallaxes
Why is the distribution of globular clusters significant?
B) Spherical symmetry indicates the position of the Milky Way center
Which of the following is FALSE?
A) The H-R diagram can be used to find the luminosity of a main sequence star, given its spectral type.
B) A star with spectral type of B is sometimes hotter than a star with spectral type A, and sometimes colder.
C) Parallax can be used to measure the distances to the nearest stars.
D) The lifetimes of stars range from a few million years for the most massive to much more than 14 billion years for less massive stars.
E) Transits and radar represent the bottom rung of the distance ladder.
B) A star with spectral type of B is sometimes hotter than a star with spectral type A, and sometimes colder.
How can we see through the dusty plane of the Milky Way disk in order to study star formation?
A) Look at infrared radiation with the Spitzer Space Telescope.
If you could convert a mass of 3 million grams (mass 3 x 106g) into pure energy, how much energy would be produced (in ergs) ? The speed of light c = 3 x 1010cm/s.
D) 2.7 x 1027ergs
In nuclear fusion, energy is produced because:
E) the mass of the reacting chemicals is larger than that of the products.
Compare a Type Ia and a Type II supernova. Which of the following is TRUE?
A) A Type Ia does not have Hydrogen in its spectrum and a Type II does.
B) A Type Ia has hydrogen in its spectrum and a Type II does not.
C) A Type Ia supernova results from the death of a massive star and a Type II from a white dwarf that accretes matter from a companion.
D) Neither a Type Ia or a Type II supernova has hydrogen in its spectrum.
E) Both Type Ia and Type II supernovae have hydrogen in their spectra.
A) A Type Ia does not have Hydrogen in its spectrum and a Type II does.
What is a T-Tauri star?
B) A type of protostar.
Molecular clouds have "what it takes" to form stars, which is:
A) lots of Hydrogen
B) some Helium
C) more than 100 times the mass of the Sun
D) all of the above
E) none of the above
D) all of the above
The Earth passes through a larger density of interstellar gas in March than in other months because
B) that is the concentration of interstellar wind particles deflected behind the Sun's path through its local medium
Which of the following will have the shortest lifetime on the main sequence?
A) main sequence star with a mass 2 times that of the Sun
B) main sequence star with surface temperature 20000 K
C) main sequence star with surface temperature 3000 K
D) main sequence star with a luminosity one tenth that of the Sun
E) the Sun
B) main sequence star with surface temperature 20000 K