Astronomy: Stars (part 2) – Flashcards
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A nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy
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nuclear fusion
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(physical chemistry) a fourth state of matter distinct from solid or liquid or gas and present in stars and fusion reactors. A gas-like state of matter consisting of a mixture of free electrons and atoms that are stripped of their electrons. The Sun is made of this stuff yo
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plasma
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The outer layer of the sun's atmosphere.
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corona
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A gaseous layer of the sun's atmosphere (extending from the photosphere to the corona) that is visible during a total eclipse of the sun
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chromosphere
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The inner layer of the sun's atmosphere that gives off its visible light
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photosphere
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The outer most layer of the sun's interior: hot gases rise and eventually cool as they approach the top.
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convection zone
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A region of very tightly packed gas in the sun's interior where energy is transferred mainly in the form of light.
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radiation zone
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An elementary particle that has little rest mass and no charge but carries energy from a nuclear reaction.
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neutrino
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Almost no light emerges from below the photosphere, so you can't see into the solar interior. However, solar astronomers using a technique called ____ can analyze naturally occurring vibrations in the sun constantly produce vibrations- rumbles that would be much too low to hear with human ears even if your ears could survive a visit to the sun's atmosphere. They are generally very, very low pitch sounds.
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helioseismology
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a system for describing stellar brightness by using numbers, called magnitudes, based on an ancient Greek way of describing the brightness of stars in the sky. This system uses apparent magnitude to describe a star's apparent brightness and absolute magnitude to describe a star's luminosity. 1 being the brightest.
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magnitude system
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O type stars have the _________ surface temperature
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highest
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Mmemonic for remembering the OBAFGKM spectral type sequence
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Oh Be A Fine Girl, Kiss Me
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Early twentieth century astronomer who catalouged the spectra of over 225,000 stars. Her most significant contribution to society was carefully categorized spectra of light emmitted from stars, allowing others who followed to build off her work
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Annie Jump Cannon
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Two stars orbiting their common center of gravity.
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binary star system
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A pair of stars we can see with a telescope as they orbit each other
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visual binary
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A graph of brightness versus time commonly used in analyzing variable stars and eclipsing binaries.
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light curve
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when stars run out of hydrogen in their centers they may also start to undergo fusion of the helium. Process takes three Helium nuclei and combines them into a carbon nucleus, releasing energy into the core (triple-alpha process)
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helium fusion
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For these larger stars, C is found in the star's spectrum as absorption lines. These stars are known as ______ _____. Strong convection drudges up carbon from the core during a star's last gasps.
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carbon stars
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Fusion reactions that fuse a helium nucleus into some other nucleus; such reactions can fuse carbon into oxygen, oxygen into neon, neon into magnesium, and so on.
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helium-capture reactions
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Ordered list of the shells a dying star can attain during fusion of heavier nuclei
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iron (inert), silicon, magnesium, neon, oxygen, carbon, helium, hydrogen
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origin of the heavy elements
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dying stars
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core-collapse of a high-mass star, elements heavier than iron generated very rapidly in explosion
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supernovae
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A celestial object of very small radius (typically 18 miles/30 km) and very high density, composed predominantly of closely packed neutrons. Such objects are thought to form by the gravitational collapse of the remnant of a massive star after a supernova explosion, provided that the star is insufficiently massive to produce a black hole.
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neutron star
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A small very dense star that is typically the size of a planet. Such an object is formed when a low-mass star has exhausted all its central nuclear fuel and lost its outer layers as a planetary nebula. Maintained by electron degeneracy pressure.
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white dwarf
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The limit to the mass of a white dwarf star, above which it cannot be supported by electron degeneracy and cannot exist as a white dwarf.
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Chandrasekhar limit
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What is the Chandrasekhar limit?
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1.4 solar masses
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A white dwarf can have an accretion disk if it formed in a _____ _______ __________
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close binary system
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Occurs when the energy produced ejects much of the white dwarf accretion disc into space.
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novae
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Occurs when an accreting white dwarf reaches the white dwarf limit, ignites runaway carbon fusion and explodes like a bomb. A(n) ____________ can occur only in a binary system, and all such events are thought to have the same luminosity. Often called a type Ia supernovae.
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white dwarf supernovae
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Iron core of massive star collapses and explodes- leaving behind either a neutron star or a black hole. NOT the same as a white dwarf supernovae.
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massive star supernovae
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The features which distinguish a white dwarf supernovae from massive star supernovae
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fades quicker, lack hydrogen lines, (all white dwarf supernovaes have) identical light curves
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A celestial object, thought to be a rapidly rotating neutron star, that emits regular pulses of radio waves and other electromagnetic radiation at rates of up to one thousand pulses per second.
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pulsar
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a binary star system in which one of the stars, or the gas associated with a star, emits x rays intensely. Thought to be close binaries with accreting neutron stars.
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X-ray binaries
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An object that produces occasional X-ray flares. Thought to be caused by mass transfer in a closed binary system
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X-ray bursters
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The location around a black hole where the escape velovity equals the speed of light; the boundary of a black hole
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event horizon
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An object in space whose gravity is so strong not even light can escape.
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black hole
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The distance from the center of an object such that, if all the mass were compressed within that region, the escape speed would equal the speed of light
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Schwarzschild radius
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A point in which matter is infinitely dense, as in the center of a black hole or the universe at the very beginning.
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singularity
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neutron star limit
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3 solar masses
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Gamma rays associated with extremely energetic explosions that have been observed in distant galaxies. They are the brightest electromagnetic events known to occur in the universe. The leading hypothesis assumes a collision in a binary system between two neutron stars or a neutron star and a black hole spiral in towards each other until they collide. This produces powerful bursts of gamma rays as they merge to form a black hole.
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gamma-ray bursts
