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ASTRO – Space

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How does the radius of the event horizon change when you ass a mass to a black hole
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It Increases
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O B A F G K M TEMPERATURE
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Hottest -Coldest
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O B A F G K M mass
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Most Massive – Least Massive
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What do we mean by the main-sequence turnoff point of a star cluster, and what does it tell us?
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-It is the spectral type of the hottest main sequence star in a star cluster -cluster’s age
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A brown dwarf is
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an object not quite massive enough to be a star
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Careful measurements reveal that a star maintains a steady apparent brightness at most times, except that at precise intervals of 73 hours the star becomes dimmer for about 2 hours. The most likely explanation is that
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the star is a member of an eclipsing binary star system
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O B A F G K M which stars are cool and dim?
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K M
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Which group represents stars of the largest radii? o b a f g k m
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F G K M
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hich group represents stars that are extremely bright and emit most of their radiation as ultraviolet light
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O B
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Which group represents stars with the longest main-sequence lifetimes
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K M
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Which group represents stars fusing hydrogen in their cores?
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Which group represents stars fusing hydrogen in their cores?
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Entire main sequence
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You observe a star and you want to plot it on an H-R diagram. You will need to measure all of the following, except the star’s ________
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Mass
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How did astronomers discover the relationship between spectral type and mass for main sequence stars
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By measuring the masses and spectral types of main-sequence stars in binary systems
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What is the approximate range of masses that newborn main sequence stars can have?
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0.1 to 150 solar masses
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Which of the following lists the stages of life for a low-mass star in the correct order
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Protostar, main-sequence star, red giant, planetary nebula, white dwarf
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Why is iron significant to understanding how a supernova occurs?
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Iron cannot release energy either by fission or fusion.
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Algol consists of a 3.7 M Sun main-sequence star and a 0.8 M Sun subgiant. Why does this seem surprising, at least at first
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The two stars should be the same age, so we’d expect the subgiant to be more massive than the main-sequence star.
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What is a protostar
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A star that is still in the process of forming
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Approximately what core temperature is required before hydrogen fusion can begin in a star?
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10 million K
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The vast majority of stars in a newly formed star cluster are ________.
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Less massive than the Sun
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What is a planetary nebula?
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Gas ejected from a low-mass star in the final stage of its life
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he ultimate fate of our Sun is to ______
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Become a white dwarf and cool in time
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After a supernova explosion, the remains of the stellar core _____
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may be either a neutron star or a black hole
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The Schwarzschild radius of a black hole depends on ________.
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only the mass of the black hole
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The maximum mass of a white dwarf is _________
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about 1.4 times the mass of our Sun
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A neutron star is ________
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the remains of a star that died in a massive star supernova (if no black hole was created)
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Pulsars are thought to be ________
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rapidly rotating neutron stars
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what is the basic definition of a black hole
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An object with gravity so strong that not even light can escape
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At the center of the Sun, fusion converts hydrogen into
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helium, energy, and neutrinos
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Which of the following correctly compares the Sun’s energy generation process to the energy generation process in human-built nuclear power plants
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The Sun generates energy by fusing small nuclei into larger ones, while our power plants generate energy by the fission (splitting) of large nuclei.
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Which of the following best explains why nuclear fusion requires bringing nuclei extremely close together?
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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.
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What do we need to measure in order to determine a star’s luminosity?
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apparent brightness and distance
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What two pieces of information would you need in order to measure the masses of stars in an eclipsing binary system?
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the time between eclipses and the average distance between the stars
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Which of these stars has the coolest surface temperature? A F K
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K
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Which of these stars is the most massive? A G M
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A
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Which of these stars has the longest lifetime A G M
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M
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Which of these stars has the largest radius? A K M
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M
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Star A is identical to Star B, except that Star A is twice as far from us as Star B. Therefore:
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Both stars have the same luminosity, but the apparent brightness of Star B is four times that of Star A
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true or false The spectral type of a star can be used to determine its distance.
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False
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Sirius is a star with spectral type A star and Rigel is a star with spectral type B star. What can we conclude about temperature?
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Rigel has a higher surface temperature than Sirius
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To calculate the masses of stars in a binary system, we must measure their ________.
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orbital period and average orbital distance
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Why is a sunflower yellow?
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It reflects yellow light.
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Blue light has higher frequency than red light. Thus, blue light has:
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higher energy and shorter wavelength than red light.
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Radio waves are a form of sound a form of light. a type of spectrum.
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a form of light.
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The set of spectral lines that we see in a star’s spectrum depends on the star’s:
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chemical composition.
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A star whose spectrum peaks in the infrared is
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cooler than our Sun.
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A spectral line that appears at a wavelength of 321nm in the laboratory appears at a wavelength of 328nm in the spectrum of a distant object. We say that the object’s spectrum is redshifted. blueshifted. skewed.
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redshifted.
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The Hubble Space Telescope obtains higher-resolution images than most ground-based telescopes because it is: Larger. closer to the stars. above Earth’s atmosphere
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Larger
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True or False green grass absorbs red light and reflects green light.
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True
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True Or False X-rays travel through space faster than radio waves.
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False
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Studying a spectrum from a star can tell us a lot. All of the following statements are true except one. Which statement is not true?
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The total amount of light in the spectrum tells us the star’s radius
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The angular separation of two stars is 0.1 arcseconds and you photograph them with a telescope that has an angular resolution of 1 arcsecond. What will you see
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The photo will seem to show only one star rather than two
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How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope?
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The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.
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Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?
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It is closer to the stars.
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The Chandra X-ray Observatory must operate in space because
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X-rays do not penetrate Earth’s atmosphere
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Which of the following is always true about images captured with X-ray telescopes?
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They are always shown with colors that are not the true colors of the objects that were photographed.
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How are wavelength, frequency, and energy related for photons of light?
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Longer wavelength means lower frequency and lower energy.
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According to modern science, approximately how old is the Sun?
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4.5 billion years
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From center outward, which of the following lists the “layers” of the Sun in the correct order?
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core, radiation zone, convection zone, photosphere, chromosphere, corona
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The overall result of the proton-proton chain is that __________
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4 H becomes 1 He + energy
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The Sun will exhaust its nuclear fuel in about ________.
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5 billion years
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The source of energy that keeps the Sun shining today is ________.
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nuclear fusion
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The Sun’s surface, as we see it with our eyes, is called the ______
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photosphere
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The Sun’s average surface (photosphere) temperature is about ________.
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5,800 K
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What is the solar wind?
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A stream of charged particles flowing outward from the surface of the Sun
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A stream of charged particles flowing outward from the surface of the SunThe fundamental nuclear reaction occurring in the core of the Sun is ______
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Nuclear fusion of hydrogen into helium
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According to the inverse square law of light, how will the apparent brightness of an object change if its distance to us triples?
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Its apparent brightness will decrease by a factor of 9.
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Assuming that we can measure the apparent brightness of a star, what does the inverse square law for light allow us to do?
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Calculate the star’s luminosity if we know its distance, or calculate its distance if we know its luminosity.
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he axes on a Hertzsprung-Russell (H-R) diagram represent _________
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Luminosity and surface temperature
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What do we mean by the main-sequence turnoff point of a star cluster, and what does it tell us?
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It is the spectral type of the hottest main sequence star in a star cluster, and it tells us the cluster’s age.
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What would you be most likely to find if you returned to the solar system in 10 billion years? a neutron star a white dwarf a black hole
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a white dwarf
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In order to predict whether a star will eventually fuse oxygen into a heavier element, you mainly want to know what fact about the star?
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its mass
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Our Sun is considered to be a ________. intermediate-mass star brown dwarf low-mass star high-mass star
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low-mass star
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what is the heaviest element that a 10 solar mass star will create in its core?
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iron
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Where was the majority o the golf on earth created?
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Supernova
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What is the upper mass limit of a neutron star Most massive a nuestron star could be
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3 Solar masses
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Which of the follwing has the smallest radius
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the event horizon of a 3.0 solar mass black hole adding mass to black hole makes for larger radius adding mass to star means smaller radius
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someone is signaling you with a green laser from just outside of the event horizon of a black hole What do you see? red light greenlight blue light
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red light
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List in they correct order of phases for a 1 solar mass star going from birth to death
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Prostar main sequnce giant planetary nebula white dwarf
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White dwarfs are typically made up of what material
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Carbon
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Which process compltey destroys the star leaving nothing behind?
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White dwarf supernova
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HOw does a Red GIant star look different from a main Sequence star of simalar mass?
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Redder & Brighter
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which of these stars are the oldest? A Temp 22,000 B Temp 9,000 C Temp 5,000 D Temp 7,000
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C (the older the star the cooler the star)
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Where would a brown dwarf be located on an H-R diagram?
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Below and to the right of the lowest part of the main sequence
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Carbon fusion occur in high-mass stars but not in low-mass stars because ________
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the cores of low-mass stars never get hot enough for carbon fusion
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Which event marks the beginning of a supernova?
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collapse of an iron core into a ball of neutrons
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A spinning neutron star has been observed at the center of a ________.
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supernova remnant
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Which is more common: a star blows up as a supernova, or a star forms a planetary nebula/white dwarf system?
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Planetary nebula formation is more common.
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You discover a binary star system in which one star is a 15 MSun main-sequence star and the other is a 10 MSun giant. How do we think that a star system such as this might have come to exist?
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The giant must once have been the more massive star, but is now less massive because it transferred some of its mass to its companion.
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What did Carl Sagan mean when he said that we are all “star stuff”?
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that the carbon, oxygen, and other elements essential to life were created by nucleosynthesis in stellar cores
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Compared to the star it evolved from, a red giant is
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cooler and brighter.
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What happens to the core of a star after it ejects a planetary nebula?
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It becomes a white dwarf.
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Compared to the star it evolved from, a newly formed white dwarf is
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hotter and dimmer.
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What types of stars end their lives with supernovae?
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stars that are at least several times the mass of the Sun
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After a supernova event occurring in a high-mass star, what is left behind?
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either a neutron star or a black hole
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A typical white dwarf is _________.
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as massive as the Sun but only about as large in size as Earth
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Which of these objects has the smallest radius?
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a 1.2 white dwarf
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Suppose that a white dwarf is gaining mass through accretion in a binary system. What happens if the mass someday reaches the 1.4 solar mass limit?
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The white dwarf will explode completely as a white dwarf supernova.
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A typical neutron star is more massive than our Sun and about the size (radius) of _________.
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a small asteroid (10 km in diameter)
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What do we mean by the event horizon of a black hole?
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It is the point beyond which neither light nor anything else can escape.
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Imagine that our Sun were magically and suddenly replaced by a black hole of the same mass (1 solar mass). What would happen to Earth in its orbit?
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Nothing—Earth’s orbit would remain the same.
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Which of these objects has the largest radius? a 1.2 white dwarf a 1.5 neutron star a 3.0 black hole
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a 1.2 white dwarf
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Which of these things has the smallest radius? a 1.2 white dwarf the event horizon of a 3 black hole the event horizon of a 10 black hole
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the event horizon of a 3 black hole
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How would a flashing red light appear as it fell into a black hole?
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Its flashes would shift to the infrared part of the spectrum.
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Which of these black holes exerts the weakest tidal forces on an object near its event horizon? 10 black hole 100 black hole 10^6 black hole
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10^6 black hole
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The more massive a white dwarf, the ________.
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smaller its radius
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The white dwarf that remains when our Sun dies will be mostly made of ________.
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carbon
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Will our Sun ever undergo a white dwarf supernova explosion? Why or why not?
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No, because it is not orbited by another star.
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Which of the following best describes what would happen if a 1.5-solar-mass neutron star, with a diameter of a few kilometers, were suddenly (for unexplained reasons) to appear in your home town?
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The entire Earth would end up as a thin layer, about 1 cm thick, over the surface of the neutron star.
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Which statement concerning black hole masses and Schwarzschild radii is not true?
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In a binary system with a black hole, the Schwarzschild radius depends on the distance from the black hole to the companion star.
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Suppose you drop a clock toward a black hole. As you look at the clock from a high orbit, what will you notice?
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Time on the clock will run slower as it approaches the black hole, and light from the clock will be increasingly redshifted.
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Suppose you know the frequency of a photon and the speed of light. What else can you determine about the photon?
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its wavelength and energy
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Which of the following best describes the fundamental difference between two different chemical elements (such as oxygen and carbon)?
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They have different numbers of protons in their nucleus.
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Suppose you watch a leaf bobbing up and down as ripples pass it by in a pond. You notice that it does two full up and down bobs each second. what is its frequency?
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They have a frequency of 2 hertz.
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If we say that a material is opaque to ultraviolet light, we mean that it _________.
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absorbs ultraviolet light
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Which forms of light are lower in energy and frequency than the light that our eyes can see?
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infrared and radio
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Suppose you look at a spectrum of visible light by looking through a prism or diffraction grating. How can you decide whether it is an emission line spectrum or an absorption line spectrum?
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emission bright lines on a dark background absorption dark lines on a rainbow background.
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Thermal radiation is defined as _________.
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radiation with a spectrum whose shape depends only on the temperature of the emitting object
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According to the laws of thermal radiation, hotter objects emit photons with _________.
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a shorter average wavelength
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Suppose you want to know the chemical composition of a distant star. Which piece of information is most useful to you?
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the wavelengths of spectral lines in the star’s spectrum
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The spectra of most galaxies show redshifts. This means that their spectral lines _________.
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have wavelengths that are longer than normal
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the two principle advantages of telescopes over eyes?
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Telescopes can collect far more light with far better angular resolution.
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The stars in our sky twinkle in brightness and color because of _________.
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turbulence in Earth’s atmosphere
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From shortest to longest wavelength, which of the following correctly orders the different categories of electromagnetic radiation?
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Gamma rays, X-rays, ultraviolet, visible light, infrared, radio
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When considering light as made up of individual “pieces,” each characterized by a particular amount of energy, the pieces are called ________.
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photons
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Visible light from a distant star can be spread into a spectrum by using a glass prism or ________.
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a diffraction grating
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An atom that has fewer electrons than protons is called a/an ________.
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ion
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What is the angular resolution of the human eye?
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About 1 arcminute, or 1/60 of a degree
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What do astronomers mean by light pollution?
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Light pollution is light from human sources that makes it difficult to see the stars at night.
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What is the purpose of adaptive optics?
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reduces blurring caused by atmospheric turbulence
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What is the purpose of interferometry?
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It allows two or more small telescopes to achieve the angular resolution of a much larger telescope.
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Fission is?
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BIg nucleus splits into 2 smaller piecies Neclear power plants
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Fusion is?
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Small nuclei stick together to make a bigger one SUN AND STARS
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A stars Brightness depends on?
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Luminisoity and Distance
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mass determines?
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how hot a star gets what element it will produce
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Iron core of massive star reaches white dwarf limit and collapses into a neutron star, causing an explosion.
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Massive star supernova:
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White dwarf in close binary system reaches white dwarf limit causing
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a total explosion
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In the Greek geocentric model, the retrograde motion of a planet occurs when:
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the planet actuall goes backwards in its orbit to earth
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Keplers laws of motion
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First law the orbit of each planets around the sun is an ellipse with the sun at one focus —– basically a planets distance from the sun changes depending on its orbit Second law as a planet moves around its orbit it sweeps out equal areas in equal times —– This means that a planet travels faster when it’s nearer to the sun and slower when it us farther from the sun Third law more distant planets orbit the sun at slower average speeds obeying the relationships —- uses a mathematical equation to prove that more distant planets move more slowly Kepler was led to believe that planetary motions were a result of force of the sun .
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Galileo observed all of the following. Which observation offered direct proof of a planet orbiting the Sun?
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Phases of venus
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One of the “nails in the coffin” for the Earth-centered universe was
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Galileo’s observations of the moons of Jupiter.
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From Kepler’s third law, a hypothetical planet that is twice as far from the Sun as Earth should have a period of
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More than 2 years
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Kepler’s second law, which states that as a planet moves around its orbit it sweeps out equal areas in equal times, means that
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planets travel faster when nearer to the sun and slower when further
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Which one of the following describes an object that is accelerating?
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A car going around a circular track at a steady 100 miles per hour.
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Compared to its angular momentum when it is farthest from the Sun, Earth’s angular momentum when it is nearest to the Sun is
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the same
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The gravitational potential energy of a contracting interstellar cloud:
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gradually transforms into other forms of energy.
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If the Moon were closer to Earth, high tides would:
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be higher than they are now.
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Which of the following best describes the origin of ocean tides on Earth?
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Tides are caused by the difference in the force of gravity exerted by the Moon across the sphere of the Earth.
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According to the universal law of gravitation, if you double the masses of both attracting objects, then the gravitational force between them will
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increase by a factor of four
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The gravitational force that the Earth exerts on the Moon is equal and opposite to that which the Moon exerts on the Earth. Therefore, according to Newton’s second law of motion,
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the Moon as a larger acceleration than the Earth, because it has a smaller mass.
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What is the celestial sphere?
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The celestial sphere is a representation of how the entire sky looks as seen from Earth.
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What is the ecliptic?
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The path the Sun appears to trace around the celestial sphere each year
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Which of the following statements does not use the term angular size or angular distance correctly?
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The angular distance between those two bright stars in the sky is about 2 meters.
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The point directly over your head is called ________.
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the zenith
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Which kind of object is the best standard candle for measuring distances to extremely distant galaxies?
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a white dwarf supernova
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Why do virtually all the galaxies in the universe appear to be moving away from our own?
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Because expansion causes all galaxies to move away from nearly all others.
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Which of these galaxies is most likely to be oldest?
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a galaxy in the Local Group
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When we observe a distant galaxy whose photons have traveled for 10 billion years before reaching Earth, we are seeing that galaxy as it was when the universe was
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4 billion years old.
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In a photo like the Hubble Deep Field (the figure in your textbook), we see galaxies in many different stages of their lives. In general, which galaxies are seen in the earliest (youngest) stages of their lives?
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The galaxies that are farthest away
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The most basic difference between elliptical galaxies and spiral galaxies is that ________.
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elliptical galaxies lack anything resembling the disk of a spiral galaxy
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Hubble’s galaxy classification diagram (the “tuning fork”) ________.
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relates galaxies according to their shapes, but not according to any evolutionary status
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Suppose we observe a Cepheid variable in a distant galaxy. The Cepheid brightens and dims with a regular period of about 10 days. What can we learn from this observation?
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We can learn the distance to the galaxy.
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In 1924, Edwin Hubble proved that the Andromeda Galaxy lay far beyond the bounds of the Milky Way, thus putting to rest the idea that it might have been a cloud within our own galaxy. How was he able to prove this?
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By observing individual Cepheid variable stars in Andromeda and applying the period-luminosity relation
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Why are white dwarf supernovae more useful than massive star supernovae for measuring cosmic distances?
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White dwarf supernovae all have roughly the same true peak luminosity, while massive supernovae come in a wide range of peak luminosities.
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What is the best way to determine a galaxy’s redshift?
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Take a spectrum of the galaxy, and measure the difference in wavelength of spectral lines from the wavelengths of those same lines as measured in the laboratory.
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Which statement below correctly describes the relationship between expansion rate and age for the universe?
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The faster the rate of expansion, the younger the age of the universe.
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What does cosmological redshift do to light?
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Stretches its wavelength
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What does Hubble’s law tell us?
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The more distant a galaxy, the faster it is moving away from us.
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If we say that a galaxy has a lookback time of 1 billion years, we mean that ________.
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its light traveled through space for 1 billion years to reach us
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Current estimates place the age of the universe at about ________.
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14 billion years
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According to current understanding, what is a quasar?
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An active galactic nucleus that is particularly bright
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The mass of a supermassive black hole thought to power a typical bright active galactic nucleus is roughly ________.
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1 billion solar masses
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What is the most accurate way to determine the distance to a nearby star?
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stellar parallax
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What is the most accurate way to determine the distance to a nearby galaxy?
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Cepheid variables
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Which of the following best summarizes what we mean by dark matter?
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matter that we have identified from its gravitational effects but that we cannot see in any wavelength of light
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Which of the following best summarizes what we mean by dark energy?
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It is a name given to whatever is causing the expansion of the universe to accelerate with time.
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What is a rotation curve?
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a graph showing how orbital velocity depends on distance from the center for a spiral galaxy