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astro111NTest3

QuestionAnswer
How do we know how old the Sun is? From ages of solar system meteorites, based on radioactive elements
Which of the following models best explains why our galaxy has spiral arms? The spiral arms are a wave of star formation caused by wave of density propagating outward through the disk of the galaxy.
As a solar mass protostar moves on to the main sequence, its surface temperature increases and its luminosity decreases
Which of the following statements about degeneracy pressure is not true? Degeneracy pressure varies with the temperature of the star.
The Sun does not generates energy primarily by nuclear fission.
The remnant left behind by a white-dwarf supernova is not a neutron star.
What happens to energy in the Sun's convection zone? Energy is transported outward by the rising of hot plasma and sinking of cooler plasma
Which main sequence star has the lowest mass? M.
From center outward, which of the following lists the "layers" of the Sun in the correct order? Core, radiation zone, convection zone, photosphere, chromosphere, corona
Based on observations, which of the following statements about stars in the Milky Way is generally true? The older the star, the lower its abundance of heavy elements.
A star's luminosity is the total amount of energy that the star radiates each second
Which main sequence star will have the shortest lifetime? O.
There is no limit to the mass with which a star can be born. True or False. False.
Which element is the dead end for cores of the most massive stars? Iron
On an H-R diagram, stellar radii ________. increase diagonally from the lower left to the upper right
Where are most heavy elements made? In stars and supernovae.
What causes the radio pulses of a pulsar? As the neutron star spins, beams of radio radiation sweep through space. If one of the beams crosses the Earth, we observe a pulse.
On a Hertzsprung-Russell diagram, where on the main sequence would you find stars that have the greatest mass? upper left
Over time, the star-gas-star cycle leads the gas in the Milky Way to ________. have a greater abundance of heavy elements
Which o the following stars are brightest at ultraviolet wavelengths? O and B stars
How does the interstellar medium obscure our view of most of the galaxy? The small mixture of dust grains in the interstellar medium absorbs visible light.
No visible light can escape a black hole, but things such as gamma rays, X-rays, and neutrinos can. True or False False.
Marks: 1 How do we know the total mass of the Milky Way Galaxy that is contained within the Sun's orbital path? By applying Newton's version of Kepler's third law (or the equivalent orbital velocity law) to the Sun's orbit around the center of the Galaxy
What type of star is our Sun? A low-mass star
How is the lifetime of a star related to its mass? More massive stars live much shorter lives than less massive stars.
Stars spend about 90% of their lifetime on the main sequence. True or False. True
The Sun is located near the edge of our galaxy, approximately 100,000 light-years from the galactic center. True or False. False
The Sun's location in the Milky Way Galaxy is ________. in the galactic disk, roughly halfway between the center and the outer edge of the disk
Identify the correct sequence of life events for a high mass star. Main sequence, red supergiant, supernova, neutron star
The Sun's average surface (photosphere) temperature is about ________. 5,800 K
The proton-proton chain converts four hydrogen nuclei into one helium nucleus plus energy. true or false true
The overall helium fusion reaction is: three helium nuclei fuse to form one carbon nucleus.
Brown dwarfs, white dwarfs, and neutrons stars are all kept from collapsing by degeneracy pressure. true or false true
What is the upper limit to the mass of a white dwarf? 1.4 solar masses
When does a star become a main-sequence star? when the rate of hydrogen fusion in the star's core is high enough to sustain gravitational equilibrium
What do we call the bright, sphere-shaped region of stars that occupies the central few thousand light-years of the Milky Way Galaxy? the galaxy's bulge
What do we mean by the interstellar medium? The gas and dust that lies in between the stars in the Milky Way galaxy
How does a black hole form from a massive star? During a supernova, if a star is massive enough for its gravity to overcome neutron degeneracy pressure in the core, the core will collapse to a black hole.
What can we learn about a star from a life track on an H-R diagram? what surface temperature and luminosity it will have at each stage of its life
What happens when a star like the sun exhausts its core hydrogen supply? Its core contracts, but its outer layers expand and the star becomes bigger and brighter.
Compared to the star it evolved from, a newly formed white dwarf is hotter and dimmer.
Marks: 1 If the distance between us and a star is doubled, its apparent brightness will decrease by a factor of four. true or false true
Which of the following is not a method astronomers use to determine the physical conditions inside the Sun? Observing X-ray images of the solar interior using satellites
Suppose you try to bring two protons close together. Because of the electromagnetic force, the two protons will repel one another
What kind of pressure supports a white dwarf? electron degeneracy pressure
What happens when the gravity of a massive star is able to overcome neutron degeneracy pressure? The core contracts and becomes a black hole.
Carbon fusion occur in high-mass stars but not in low-mass stars because ________. the cores of low-mass stars never get hot enough for carbon fusion
Compared to the star it evolved from, a red giant is cooler and brighter.
Created by: zemca
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