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| Plasma in which all the atoms or molecules have ben ionized. Sun is composed of it |
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| The amount of light reaching us per unit area from a luminous object; often measured in unites of watts/m^2 |
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| Total amount of light energy produced. Often called luminosity |
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| A large, bright feature extending outward from the Sun's surface. |
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| Blotches on the Sun's surface that appear darker than the surrounding regions. Cooler and darker. |
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A way of classifying a star by the lines that appear in its spectrum; it is related to surface temperature. The basic spectral types are designated by a letter (OBAFGKM, with O for the hottest starts and M for the coolest) and are subdivided with numbers from 0 through 9.
(Oh be a fine guy, kiss me) |
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| A star system containing two stars orbiting around their common center of mass. Brighter star is called the primary and the other is its companion, comes, or secondary. |
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| Change in brightness with time. |
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| The dramatic brightening of a star that lasts for a few weeks tand then subsides; occurs when a burst of hydrogen fusion ignites in a shell on the surface o an accreting white dwarf in a binary star system. |
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| Describes a state of balance in which the force of gravity pulling inward is precisely counteracted by pressure pushing outward. |
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| Hertzsprung-Russell Diagram |
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| A graph plotting individual stars as points, with stellar luminosity on the vertical axis and spectral type (or surface temperature) on the horizontal axis. |
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| (luminosity class V) The prominent line of points running from the upper left to the lower right on an H-R diagram; main sequence stars shine by fusing hydrogen in their cores. |
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Cool, dense intersellar clouds in which the low temperatures allow hydrogen atoms to pair up into hydrogen molecules (H2)
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| An object too small to become an ordinary star because electron degeneracy pressure halts its gravitational collapse before fusion becomes self-sustaining; brown dwarfs have mass less than 0.08M |
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| The hot, compact corpes of low-mass starts, typically with a amass similar to the Sun compressed to a volume the size of the Earth. |
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| (Luminosity class III) Stars that appear just below the supergiants on the H-R diagram because they are somewhat smaller in radius and lower in luminosity. |
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(Luminosity class I) The very large and very bright stars that appear at the top of an H-R diagram
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| The maximum possibel mass for a white dwarf, which is about 1.4M(sun) |
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| The glowing cloud of gas ejected from a low mass star at the end of its life. |
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| The compact corpse of a high mass star left over after a supernova; typically conatins a mass comparable to the sun in a volume must a few kilometers in radius. |
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| A neutron star from which we see rapid pulses of radiation as it rotates. |
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| Witnessed on Earth in 1987. It was the nearest supernova seen in nearly 400 years and helped astronomers refine the ones of supernovae |
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| Used both as the name of our galaxy and to reference the band of light we see in the sky when we look into the plane of the Milky Way |
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| The nearest large spiral galaxy to the Milky Way. |
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| Galaxies that look like flat, white disks with yellowish bulges at their centers. The disks are filled with cool dust and gas and interspereed with hotter ionized gas, and usually display to be autiful spiral arms. |
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