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

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