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111 Cards in this Set
- Front
- Back
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In a neutron star, the core is
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made of compressed neutrons in contact with each other.
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From the viewpoint of an observer in the orbiting rocket, what happens to time on the other rocket as it falls toward the event horizon of the black hole?
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Time runs increasingly slower as the rocket approaches the black hole.
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As the falling rocket plunges toward the event horizon, an observer in the orbiting rocket would see that the falling rocket __________.
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slows down as it approaches the event horizon, and never actually crosses the event horizon
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If you were inside the rocket that falls toward the event horizon, you would notice your own clock to be running __________.
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at a constant, normal rate as you approach the event horizon
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If you were inside the rocket that falls toward the event horizon, from your own viewpoint you would __________.
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accelerate as you fall and cross the event horizon completely unhindered
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The average density of neutron stars approaches:
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about 1017 kg/m3, similar to the density of atomic nuclei.
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What compelling evidence links pulsars to neutron stars?
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Only a small, very dense source could rotate that rapidly without flying apart.
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You would expect millisecond pulsars to be
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part of a binary system.
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The densely packed neutrons of a neutron star cannot balance the inward pull of gravity if the total mass is
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greater than Schwartzschild's limit of 3 solar masses.
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An observer on a planet sees a spaceship approaching at 0.5c. A beam of light projected by the ship would be measured by this observer to travel at
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c
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The equivalence principle says that a person in an elevator that is in freefall feels the same acceleration as
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a person in space, far from any gravitational source accelerating at g
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As a spaceship nears an event horizon, a clock on the spaceship (as viewed by a person watching from a distant platform) will be observed
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to run slowly
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Which of these does not exist?
a million solar mass black hole a 6 solar mass black hole a 6.8 solar mass neutron star a 1.0 solar mass white dwarf a 0.06 solar mass brown dwarf |
a 6.8 solar mass neutron star
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X-ray bursters occur in binary star systems. The two types of stars that must be present to make up such an object are
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a main sequence or giant star and a neutron star in a mass transfer binary.
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The largest known black holes
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lie in the cores of the most massive galaxies
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Two important properties of young neutron stars are
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extremely rapid rotation and a strong magnetic field
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The mass range for neutron stars is
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1.4 to 3 solar masses.
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What is Cygnus X-1?
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the leading candidate for an observable black hole binary system
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A star (no matter what its mass) spends most of its life
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as a main sequence star
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What spectral type of star that is still around formed longest ago?
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M
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Which of the following elements contained in your body is NOT formed in the cores of stars during thermonuclear fusion?
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hydrogen
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What temperature is needed to fuse helium into carbon?
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100 million K
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The "helium flash" occurs at what stage in stellar evolution?
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red giant
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What inevitably forces a star like the Sun to evolve away from being a main sequence star?
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Helium builds up in the core, while the hydrogen burning shell expands
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Just as a low-mass main sequence star runs out of fuel in its core, it actually becomes brighter. How is this possible?
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The core contracts, raising the temperature and increasing the size of the region of hydrogen shell-burning
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What is a planetary nebula?
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the ejected envelope, often bipolar, of a red giant surrounding a stellar core remnant
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Compared to our Sun, a typical white dwarf has
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about the same mass and a million times higher density.
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What characteristic of a star cluster is used to determine its age?
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the main sequence turnoff
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In globular clusters, the brightest stars will be
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red supergiants.
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Noting the turnoff mass in a star cluster allows you to determine its
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age
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Mass transfer in binaries occurs when one giant swells to reach the
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Roche Lobe
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Compared to a cluster containing type O and B stars, a cluster with only type F and cooler stars will be
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older
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That brighter Sirius A weighs 3 solar masses, but the white dwarf Sirius B is only about one solar mass implies
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that the collapsed companion transferred mass to Sirius A.
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A surface explosion on a white dwarf, caused by falling matter from the atmosphere of its binary companion, creates what kind of object?
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nova
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The Chandrasekhar mass limit is
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1.4 solar masses
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An iron core cannot support a star because
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iron cannot fuse with other nuclei to produce energy.
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Most of the energy of the supernova is carried outward via a flood of
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neutrinos.
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In neutronization of the core, a proton and an electron make a neutron and a
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neutrino
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What made supernova 1987a so useful to study?
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We saw direct evidence of nickel to iron decay in its light curve.
It occurred after new telescopes, such as Hubble, could observe it very closely. In the Large Magellanic Cloud, we already knew its distance. Its progenitor had been observed previously. All of the above are correct |
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The supernova that formed M-1, the Crab Nebula, was observed in
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1054 AD by Chinese and other oriental and mid eastern astronomers.
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Which of these is the likely progenitor of a type I supernova?
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a mass-transfer binary, with the white dwarf already at 1.3 solar masses
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Which of these is the likely progenitor of a type II supernova?
two white dwarfs in a contact binary system a contact binary, with the neutron star at 2.3 solar masses an evolved blue supergiant that is about to experience the helium flash an evolved red giant which is just starting to make silicon in its core a mass-transfer binary, with the white dwarf already at 1.3 solar masses |
an evolved red giant which is just starting to make silicon in its core
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If it gains sufficient mass, a white dwarf can become a
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type I supernova.
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Supernova remnants differ from star forming regions because, although there is ionized hydrogen in both, supernova remnants
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contain no ionizing stars.
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A recurrent nova could eventually build up to a
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Type I supernova.
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The heaviest nuclei of all are formed
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by neutron capture during a type II supernova explosion.
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The making of abundant iron nuclei is typical of
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type II supernovae
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Nearly all the elements found in nature were formed inside stars, except for
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hydrogen and helium
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What are the two most important intrinsic properties used to classify stars?
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luminosity and surface temperature
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What physical property of a star does the spectral type measure?
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temperature
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The most famous G type star is
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the sun
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Stars that have masses similar to the Sun's, and sizes similar to the Earth are
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white dwarfs
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Which of the following is the most common type of star?
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low mass main sequence
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What is the typical main sequence lifetime of a G-type star?
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10 billion years
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Interstellar gas is composed of
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90% hydrogen, 9% helium by weight
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Due to absorption of shorter wavelengths by interstellar dust clouds, distant stars appear
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redder
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Which is the least dense?
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interstellar dust
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Most interstellar clouds are
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much bigger than our solar system
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What is the primary visible color of an emission nebula?
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red due to ionized hydrogen atoms
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What two things are needed to create an emission nebulae?
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hot stars and interstellar gas, particularly hydrogen
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A reflection nebula is caused by
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starlight scattered by dust particles
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Astronomers use roman numerals to indicate the ionization state of a gas. Ionized hydrogen is indicated by which of the following symbols?
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HII
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The average temperature of the typical dark dust cloud is about
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100 K
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Interstellar dust clouds are best observed at what wavelength?
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Radio and infrared
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The Local Bubble was probably created by
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a nearby supernova perhaps 300,000 years ago, brighter than the Full Moon
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What information does 21 cm radiation provide about the gas clouds?
their density their temperature their distribution their motion all of these |
all of these
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Neutral hydrogen is most obvious in the electromagnetic spectrum at
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21 cm in the radio region.
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Why is 21-cm radiation so important to the study of interstellar matter and the Galaxy?
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Emitted by hydrogen, it passes through interstellar dust and lets us to map the entire Galaxy.
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Which of the following have not yet been observed in space?
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DNA
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Our Sun, along with most of the stars in our neighborhood probably formed about
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billions of years ago
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Which event marks the birth of a star?
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fusion of hydrogen atoms into helium atoms
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What happens when an interstellar cloud fragment shrinks?
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Pressure rises.
Temperature rises. It first becomes opaque. Density rises. all of the above |
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A typical protostar may be several thousand times more luminous than the Sun. What is the source of this energy?
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from the release of gravitational energy as the protostar continues to shrink
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At what stage of evolution do T Tauri stars occur?
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when a protostar is on the verge of becoming a main sequence star
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Most stars in our part of the Galaxy are formed
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in open clusters of a few dozen.
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A collapsing cloud fragment that will form a star of one solar mass (like our Sun) has a mass of about
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2 solar masses
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What are the two most important intrinsic properties used to classify stars?
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luminosity and surface temperature
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Jupiter is noticeably oblate because
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it rotates rapidly
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How does the mass of Jupiter compare with that of the other planets?
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It is twice as massive as all other planets combined
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What evidence do we have that Jupiter must have a substantial solid core under the thick clouds?
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Jupiter's disk is less oblate than it should be, if it were only hydrogen and helium.
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Essentially, the Great Red Spot is
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a large cyclonic storm (hurricane).
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What is the probable source of the day-to-day variations in Jupiter's belts and zones?
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differential rotation and the underlying zonal flow
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The reason the jovian planets lost very little of their original atmosphere is due to their
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large mass
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Together which two gases make up 99% of Jupiter's atmosphere?
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Hydrogen and Helium
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How does the heat Jupiter radiates compare to the energy it receives from the Sun?
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Jupiter radiates back into space about twice the energy it gets from the Sun
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How does the heat Jupiter radiates compare to the energy it receives from the Sun?
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Jupiter radiates back into space about twice the energy it gets from the Sun
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What is the source of Jupiter's nonthermal radio radiation?
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metallic hydrogen swirling in the planet's interior
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What would Jupiter have needed to have become a star?
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more mass
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What is thought to be the cause of Io's volcanos?
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tidal stresses from both Jupiter and Europa
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Which of the Galilean moons is the densest and most geologically active?
Callisto |
IO
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What is the origin of the jovian moons?
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The four Galilean moons formed with Jupiter, most others were later captures.
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Which of the jovian moons is the largest and also the largest moon in the solar system, even bigger than Mercury?
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Ganymede
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One of the discoveries made by the Voyager probes while near Jupiter was
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a thin ring of dust around the equator.
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The most abundant element in Saturn's atmosphere is
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hydrogen
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Saturn's cloud surface appears more uniform than Jupiter's because
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the cloud layers are thicker, allowing fewer holes to see the colorful layers
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Why does the atmosphere of Saturn appear to have only half the helium content of Jupiter?
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Much of Saturn's helium has differentiated towards its center.
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What are Saturn's rings?
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small icy particles moving in orbit around Saturn
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what does ionized helium, He II, contain
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He nucleus and one electron
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What is an H II region?
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a region where the hydrogen gas is mostly ionized
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what is the helium flash?
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explosive onset of helium to make carbon
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what is happening in the interior of a star that is on the main sequence on the H-R diagram?
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the star is generating internal energy by hydrogen fusion
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what causes formation of bipolar planetary nebulae?
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a progenitor star in a binary system
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in which phase of a stars life is it converting He to C?
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horizontal branch
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The age of a cluster can be found by:
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determining the turn off point of the main sequence
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Why do globular clusters contain stars with fewer metals(heavy elements) compared to open clusters
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open clusters have formed after in the evolution of the universe after considerable more processing
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what is the remnant left over from a type Ia(carbon detonation) supernova
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no remnant just the expanding shell
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what is the heaviest element produced by steady fusion in the core of a massive star?
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iron
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all the following atoms have a total of 4 nucleons(protons or neutrons) which of the following has the smallest mass
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4 hydrogen atoms
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what is the remnant left over from a GRB
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a black hole + expanding shell
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what was the subject of the great debate about GRBs that went on for -30 years
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if they were galactic or extragalactic in origin
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where do most GRBs occur?
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in star forming regions
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