modern astronomy – Flashcards
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how old is the universe
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13.8 billion years
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how much larger is the diameter of earth than the diameter of the moon
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4 times
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how much larger is the diameter of the sun than the diameter of earth
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108 times
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how large is the diameter of the milky way
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100,000 ly
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what are the largest known structures in the universe
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filaments and voids
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(blank) penetrates the earth's atmosphere to reach its surface
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visible light and radio waves
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radio waves have poor resolving power because
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they have long wavelengths
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radio telescopes are important to astronomy because
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they can detect cool hydrogen
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this technique uses high-speed computers to monitor atmospheric distortions and adjust the optics of a telescope to partially compensate for the seeing
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adaptive optics
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what is the temperature of "absolute zero" on kelvin and celsius? what occurs at this temperature?
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0K and -273.15C, all motion/vibration stops
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the absorption lines in the visible portion of the spectrum of a star that are produced by hydrogen are called
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the balmer series
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order of star class based on temperature (hottest to coldest)
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OBAFGKM
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what are the two most abundant elements in the universe
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helium and hydrogen
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what are the 2 atmospheric layers of the sun's atmosphere and which is the largest
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photosphere, chromosphere, and corona the corona is the largest
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high temperatures are required to fuse H nuclei because (blank) one another because their (blank) electric charges
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repel and positive
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neutrinos are created in reaction in which part of the sun
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photosphere
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what effect does the formation of negative hydrogen ions in the sun's photosphere have on solar observation
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the extra electrons absorbs different wavelength photons making the photosphere opaque
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at what energy level are the electrons in hydrogen gas at temperature of 25,000K
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most are in levels higher than energy level 2
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what electron energy level transition corresponds to a hydrogen atom absorbing a visible light photon that has a wavelength of 656 nm
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the electron makes the transition from energy level 2 to level 3
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what is not considered in making a simple stellar model
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magnetic field
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why is there a lower mass limit of .08 solar masses for main-sequence stars
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objects below this mass are not hot enough to fuse normal hydrogen
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which type of telescope are most modern telescopes
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reflecting
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how many more years is the sun expected to live and will it go supernova
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5 billion and no
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what is believed to be the source of the gravitational waves detected by ligo
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two black holes orbiting then merging into one
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a star's luminosity depends only on the star's
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temperature and diameter
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absolute visual magnitude is
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the apparent magnitude of a star observed from a distance of 10 pc
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giant stars are larger in diameter than the sun because
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they are more luminous but have about the same temperature
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compared with the spectral lines in the solar spectrum, lines in a supergiant spectrum are
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narrower
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the most common stars are
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lower main sequence stars (ie red dwarfs)
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how is a luminosity class assigned to a star
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by studying the absorption lines in the spectrum of the star
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the most accurate way to determine the surface temperature of a star is to study
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the pattern of absorption lines from various atoms
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in the core of a main sequence star, gas pressure (blank) the weight of the overlying material
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balances
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the energy emitted from the surface of a main sequence star is (blank) the energy generated in the core
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equal to
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as a star like the sun exhausts hydrogen in its core, the outer layers of the star
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becomes cooler and more luminous
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giants and supergiants are rare because
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the giant and supergiant stage is very short
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what element is the endpoint of nuclear fusion processes in a large star to that any element beyond this element won't undergo fusion no matter how big the star is
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iron
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an older star cluster will have (blank) than a younger star cluster
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fewer luminous stars
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open clusters tend to be (blank) than globular clusters
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younger and contain fewer stars
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why is it difficult to find out how common the most luminous stars are
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because they are rare
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why is it difficult to find out how common the least luminous stars are
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because most of them are so dim
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what prevents gravity from shrinking a white dwarf to a smaller size
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degenerate electrons
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what prevents gravity from shrinking a neutron star to a smaller size
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degenerate neutrons
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what statement accurately describes some observed properties of supernovae type 1a and supernovae type 2
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supernovae type 2 have hydrogen lines in their spectra and supernovae type 1a are more luminous
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name the luminosity classes
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1a bright supergiants, 1b supergiants, 2 bright giants, 3 giants, 4 subgiants, 5 main sequence
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what is the temperature of the sun
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5800K
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granulation is caused by
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rising gas below the photosphere
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modern astronomers suspect the corona is heated by
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the solar magnetic field
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what solved the "solar neutrino problem"
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scientists determined that the neutrinos oscillated between three different states
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which element is the physical basis for life
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carbon
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on earth whus carbon based life more successful than silicon based life
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carbon molecules chains are stronger and more stable
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how are the instructions for life stored in DNA molecules
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as a sequence of base pairs
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why must DNA instruction change for a species to survive
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to adapt to changes in the environment
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how may intelligence have began
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by species developing multiple escape strategies
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what is the period when fish first appeared
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devonian about 400 million years ago
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dinosaurs disappear at the end of what period
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cretaceous about 75 million years ago
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the stars most likely to have inhabited planets are
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spectral type "G" to "K" main sequence stars
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the DNA molecules contain 6 different bases
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false
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the miller experiment created synthetic DNA
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false
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around what type of object was the first extrasolar planet found
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pulsar
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what statements are true about life
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mutations can be caused by damaged DNA, life on earth is carbon based, genetic information is passed to generations through DNA, DNA splits with cells
