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54 Cards in this Set
- Front
- Back
The region of the Sun that contains sunspots and granulation is the
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photosphere
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The region of the Sun that can be seen easily with the naked eye only during a total solar eclipse is the
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corona
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The region of the Sun that is 1.7 times hotter than the surface and is the primary source of ultraviolet (UV) radiation is the
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chromosphere
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The surface temperature of the Sun is approximately
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5,800 K
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When we observe the Sun in visible light, sunspots appear dark because
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they are cooler than the surrounding photosphere by about 2,000 K
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A blackbody curve shows the wavelength peak of the Sun's radiation is in the middle of the ___ region of the electromagnetic spectrum
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visible
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The solar corona is so hot it emits mainly ___ radiation
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x-ray
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The temperature of the Sun's ___ is about 15 x 10^6 k
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core
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Solar ___ is a flow of energetic particles constantly streaming outward from the Sun
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wind
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Solar ____ is the name given to a filament projecting outside the lib of the Sun wehre we can see it against the black background of space. These filaments are huge and can last for days
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prominence
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The sunspot cycle averages about ___ years long
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11
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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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Solar energy leaves the core of the Sun in the form of
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photons
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Our Sun is of spectral type ___
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G
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Fusion in the sun works by the process known as the ___
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proton-proton chain
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Which one of the following star types is MOST like the sun
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F9 dwarf
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The magnitude a star would have if it were placed at a standard distance of 10 parsecs is its
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absolute magnitude
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A temperature-luminosity diagram of stars usually includes a diagonal band called the
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main sequence
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A binary star that varies in brightness as one component (Star A) passes in front of the other (Star B) is a
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eclipsing binary
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The MAIN value in the study of binary stars is the ability it gives astronomers to determine accurately the ___ of each star
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mass
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The period-luminosity relation applies to ___, supergiant stars that are very useful in measuring distances to nearby galaxies (Polaris is an example)
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Cepheid variables
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Star clusters with irregular shapes, composed of up to several thouseand stars, and containing relatively young stars are called ___ clusters
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open
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Star clusters with tight, spherical shapes, composed of up to a million stars, and containing old stars and little gas are called ___ clusters
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globular
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When thermal pressure outward balances gravity's inward pull on the gas in a star, we call this condition ___equilibrium
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hydrostatic
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Low-mass stars (like the Sun) are both with ___ or fewer solar masses
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2
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A stellar-sized hot body that derives its energy from an ongoing free-falling gravitational collapse (but not from thermonuclear reactions) is called a
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brown dwarf
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A star's main-sequence lifetime is the time the star spends on the main sequence as a
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hydrogen-fusing star
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Compared with low-mass stars, high-mass stars have main-sequence lifetimes that are
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a lot shorter
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___ pose the greatest hazard to communications satellites in Earth orbit
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Protons from the Sun
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Which one of the following is NOT a property of a star like the Sun when it is in its red giant phase
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Its lifespan at this stage is 10 million years of .1% of its stay on the main sequence
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Near the end of the red giant phase, when such a star becomes unstable, it may eject shells of gas into space, forming a
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planetary nebula
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The pressure that keeps a white dwarf from collapsing further as it cools comes from
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degeneracy pressure of packing electrons too closely
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A white dwar contains approximately the mass of ___ within the volume of the Earth
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The Sun
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The Chandrasekhar limit says that a white dwarf's mass cannot exceed ___ times the mass of the SUn, or the white dwarf will become too unstable and explode
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1.4
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If, after a supernova, the stellar core is less than 2.5-3 solar masses, the result will probably be a
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neutron star
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In descending order -hottest to coolest- the spectral classes are
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OBAFGKM
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Neutron stars pack the mass of the Sun (or greater) into an object that has a diameter of about
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10 km (half the length of Manhattan Island)
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In a black hole, the radius of the event horizon is called the ___ radius
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Schwarzchild
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Though no light escapes from a black hole, the existence of these objects can be inferred from X-ray observations of hot gas surrounding them in ___ disks
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accretion
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Supermassive black holes probably exist in
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the centers of most galxies and globular clusters
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As a red giant, a star will initiate hydrogen shell burning. Hydrogen shell buring proceeds at a higher rate than core hydrogen fusion did, resulting in the star becoming larger in radius and
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more luminous
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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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Which one of the following statements about black holes is NOT true
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A spaceship passing near a 10 solar mass black hole is much more likely to be destroyed than a spaceship passing at the same distance from the center of a 10 solar mass main-sequence star
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Which statement about pulsars is NOT thought to be true
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Pulsars can form only in close binary systems
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Stars like the Sun have two internal zones that tranpsort energy from the core to the surface. Name these two zones
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convection and radiation
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White dwarfs are dense, hot, inert cores of low-mass stars made primarily of the element carbon, which requires a temperature of ___ to begin fusion. Low-mass stars do not have enough mass to reach such a high temperature
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600 Million K
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The more massive a white dwarf, the
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smaller is its radius
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An isolated brown dwarf will
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remain a bown dwarf forever
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A star's position on the main sequence is fixed by one, fundamental property-the star's
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mass
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Degeneracy pressure prevents objects with masses below about ___ from becoming true stars
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.08 Msun
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Solar activity includes
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all of the above
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Aside from H2 and He, the MOST abundant "heavy" molecule found in molecular clouds is
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CO
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In a big molecular cloud, about half of teh elements heavier than helium are found in
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microscopic, solid grains of interstellar dust
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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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