ASTRON 0089: Exam 2
72 Cards in this Set
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luminosity
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the amount energy a star produces each second
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proton-proton chain
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the process that occurs during fusion when four hydrogen atoms combine to produce one helium atom and some excess energy
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thermonuclearfusion
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when extreme temperatures cause nuclear fusion to occur
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hydrostatic equilibrium
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when the outward pressure from a star's core is equal to the inward gravitational pull
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radiative zone
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the area of the suns core that primarily uses radiative diffusion to transfer energy
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radiative diffusion
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the random migration of a star's core based photons outward
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convection
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the tendency of hot material to rise and cold material to sink causing transfer of energy
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neutrino
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a very low-mass particle formed in solar fusion that only reacts weakly with matter
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heliosiesmology
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the study solar vibrations and tremors
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photosphere
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lowest layer of the solar atmosphere
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granules
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a surface division of a star that is created by convection
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chromosphere
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the layer of less dense, higher temp gases above the photosphere
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spicules
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pointed jets on top of the sun's atmosphere found in the chromosphere
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corona
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the outermost layer of the solar atmosphere
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coronal holes
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large regions in the corona that are cooler than the surrounding gas and produce solar wind due to the sun's magnetic field
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solar wind
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constant emission of charged particles due to the magnetic fields influence on the corona
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sunspots
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relatively cool spots of the sun's surface that are produced by local concentrations of the magnetic field
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sunspot cycle
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the 22 year full cycle that occurs because the equator of the sun rotates faster than the poles
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Zeeman Effect
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the splitting of absorption lines that allow for measurement of the solar magnetic field
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magnetic-dynamo model
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the features of the solar surface are created by changes in the solar magnetic field
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differential rotation
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the sun rotates faster at the equator than it does at the poles
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plasma
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high temperature physical state of matter in which atoms lose their electrons
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prominences
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huge, arching columns of gas that protrude out of the solar surface
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solar flare
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violent explosions of hot gas and energy from the solar surface
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coronal mass ejection
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a particularly large and incredibly powerful solar flare
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aurora
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charged particles impacting the upper atmosphere causing visible light to be produced
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stellar parallax
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the apparent change in position of a star due to Earth's motion around our sun and is used to measure the distance to nearby stars
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1 parsec
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3.26 light years
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apparent magnitude
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how bright a star appears from the surface of the earth
- the lower the number the brighter the star
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absolute magnitude
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the magnitude of a star if it was exactly 10 parsecs away
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iverse-square law relationship
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apparent brightness of a star that can be measured is inversely proportional to the square of the distance from the observer to the source
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spectral classes
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the categorization of stars determined by the details of their spectrum
OBAFGKM
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brown dwarf
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a star that is too small to sustain thermonuclear fusion
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Stefan-Boltzmann Law
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when the temp of a star increases the energy output increases
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double stars
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stars that fall along nearly the same line of sight but are actually at very different distances from us
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binary stars
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two stars that revolve around each other as a result of their mutual gravitational attraction
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center of mass
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balance point of binary system of stars
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Hertzsprung-Russell Diagram
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graph of the luminosity and surface temperature of stars that assigns them each a spectral class based upon their surface temperatures
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main sequence stars
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the general curve of stars that are found on a Hertzsprung-Russell Diagram
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mass-luminosity relations
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the greater the mass of a star, the greater its luminosity, its surface temp and its radius
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spectroscopic parallax
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the process of inferring distance to a main-sequence star based on its apparent magnitude and spectral classification
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interstellar medium
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the gas and dust that fills the vast space between the stars in a galaxy
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nebula
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large clouds of gas and dust that are the birthplaces of stars
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emission nebula
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glowing, ionized clouds of gas, powered by ultraviolet light that they absorb from nearby hot stars
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dark nebula
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extremely dense nebula that appear opaque and black out the starlight behind them
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reflection nebula
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bluish glowing in nebula caused by reflected starlight
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protostar
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the earliest stages of star birth caused by contractions of large gas clouds in nebulae
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T Tauri Stars
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protostars that have varying emission lines and spectra due to ejection of stellar material that causes changes in luminosity
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circumstellar accretion disk
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a rapidly rotating disk of material that gradually falls inward as it orbits a starlike object
-usually seen around a protostar as gravity condenses the surrounding gas
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Population II Stars
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first-generation stars formed in the very early galaxy and are metal poor
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protoplanetarydisks (proplyds)
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the dusty material left over after the birth of a star that forms the surrounding celestial objects such as planets
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Population I Stars
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stars formed from the remains of other stars and are metal rich
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triple alpha process
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when three helium atoms combine to form a carbon nucleus repeatedly in the core of a dying star
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helium flash
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in the smaller red giants the fusion of helium into carbon happens instantaneously at a certain point in the end of star's life
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degenerate-electron pressure
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core of a dying star is supported by the pressure of degenerate electrons
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asymptomatic giant branch stars (AGB)
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the second red giant phase after the helium has been burnt away, when the core contracts and the envelope expands causing the star to be much more luminous
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thermal pulses
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periodic eruptions in the helium fusion shell in an aging giant star that eventually exposes the hot dense inner core of the star
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planetary nebula
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faintly luminous cloud of gas surrounding a giant star
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white dwarf
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a very dense, very bright star about the same mass of the sun but only a hundredth of its diameter
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Solar Diameter
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1.4x10^6
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Solar Mass
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2.0x10^30
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Solar Surface Temperature
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5,800 K
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Solar Core Temperature
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15,000,000 K
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Solar Luminosity
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3.90x10^26
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Inverse-Square Law Formula
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b=L/4(pi)d^2
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extinction
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when dust absorbs light
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reddening
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when light passes through dust it becomes redshifted
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Hayashi Track
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pre-main sequence evolution
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Star Cluster
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a group of stars that are close to each other and most of the time are the same age
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Globular Cluster
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an older cluster of stars with a more spherical shape
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open cluster
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a younger group of stars that have no definite shape
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OB Association
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a cluster of hot stars that are predominantly spectral types O and B
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