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32 Cards in this Set
- Front
- Back
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constellations
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Imaginary patterns of stars.
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spectrograph
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A device that breaks light into colors and produces an image of the resulting spectrum.
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apparent brightness
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A star’s brightness as seen from Earth.
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absolute brightness
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A star’s brightness if it were at a standard distance from Earth.
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light-year
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The distance that light travels in one year, about 9.5 million million kilometers.
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parallax
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The apparent change in position of an object when you look at it from different places.
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Hertzsprung-Russell diagram
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A graph relating the surface temperatures and absolute brightnesses of stars.
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main sequence
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More than 90 percent of the stars in the H-R diagram form this diagonal area.
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nebula
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A large cloud of gas and dust spread out in an immense volume.
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protostar
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A contracting cloud of gas and dust with enough mass to form a star.
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red giant or a supergiant
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When a star begins to run out of fuel, its core shrinks and its outer portion expands and the stat becomes one of these.
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white dwarf
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The blue-white core of the star that is left behind.
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supernova
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The explosion of a supergiant.
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neutron stars
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The remains of high-mass stars.
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pulsar
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A rapidly spinning neutron star, short for pulsating radio sources.
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black hole
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An object with gravity so strong that nothing, not even light, can escape.
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binary stars
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Star systems that have two stars.
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eclipsing binary
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A system in which one star periodically blocks the light from another.
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open clusters
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A cluster with a loose, disorganized appearance and contain no more than a few thousand stars. They often contain many bright supergiants and much gas and dust.
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globular clusters
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Large groupings of older stars. They are round and densely packed with stars—some may contain more than a million stars.
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galaxy
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A huge group of single stars, star systems, star clusters, dust, and gas bound together by gravity.
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spiral galaxies
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Galaxies with a bulge in the middle and arms that spiral outward, like pinwheels.
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elliptical galaxies
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Look like round or flattened balls. These galaxies contain billions of stars but have little gas and dust between the stars.
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irregular galaxies
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Galaxies that do not have regular shapes.
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quasars
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Distant, enormously bright objects that look almost like stars. Astronomers have concluded that these objects are active young galaxies with giant black holes at their centers
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big bang
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The initial explosion that resulted in the formation and expansion of the universe.
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Hubble’s law
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States that the farther away a galaxy is, the faster it is moving away from us.
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cosmic background radiation
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The leftover thermal energy or radiation from the big bang.
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solar nebula
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A large cloud of gas and dust such as the one that formed our solar system.
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planetesimals
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Small asteroid-like bodies that formed the building blocks of our planets.
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dark matter
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Matter that does not give off electromagnetic radiation, but is abundant in the universe.
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dark energy
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A mysterious new force causing the expansion of the universe to accelerate.
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