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42 Cards in this Set
- Front
- Back
electromagnetic radiation
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energy that can travel through space in the form of waves.
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visible light
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electromagnetic radiation that can be seen with the unaided eye.
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wavelength
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the distance between the crest of one wave and the crest of the next wave.
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spectrum
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the range of wavelengths of electromagnetic waves.
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optical telescope
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a telescope that uses lenses or mirrors to collect and focus visible light.
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refracting telescope
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a telescope that uses convex lenses to gather and focus light.
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convex lens
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a piece of transparent glass curved so that the middle is thicker than the edges.
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reflecting telescope
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a telescope that uses a curved mirror to collect and focus light.
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radio telescope
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a device used to detect radio waves from objects in space.
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observatory
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a building that contains one or more telescopes.
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constellation
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an imaginary pattern of stars in the sky.
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spectograph
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an instrument that separates light into colors and makes an image of the resulting spectrum.
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apparent brightness
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the brightness of a star as seen from Earth.
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absolute brightness
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the brightness a star would have 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 seen from different places.
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Hertzsprung-Russell diagram
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a graph relating the surface temperatures and absolute brightness of stars.
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main sequence
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a diagonal area on an H-R diagram that includes more than 90% of all stars.
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nebula
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a large cloud of gas and dust in space, 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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planetary nebula
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a huge cloud of gas that is created when the outer layers of a red giant star drift out into space.
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white dwarf
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the blue-white hot core of a star that is left behind after its outer layers have expanded and drifted into space.
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supernova
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the brilliant explosion of a dying supergiant star.
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neutron star
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the small, dense remains of a high-mass star after a supernova.
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pulsar
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a rapidly spinning neutron star that produces radio waves.
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black hole
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an object whose gravity is so strong that nothing, not even light, can escape.
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binary star
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a star system with two stars.
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eclipsing binary
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a binary star system in which one star periodically blocks the light from the other.
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open cluster
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a star cluster that has a loose, disorganized appearance and contains no more than a few thousand stars.
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globular cluster
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a large, round, densely-packed grouping of older stars.
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galaxy
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a huge group of single stars, star systems, star cluster, dust, and gas bound together by gravity.
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quasar
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an enormously bright, distant galaxy with a giant black hole at its center.
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spiral galaxy
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a galaxy with a bulge in the middle and arms that spiral outward in a pinwheel pattern.
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elliptical galaxy
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a galaxy shaped like a round or flattened ball, generally containing only old stars.
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irregular galaxy
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a galaxy that does not have a regular shape.
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universe
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all of space and everything in it.
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scientific notation
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a mathematical method of writing numbers using powers of ten.
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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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the observation that the further away a galaxy is, the faster it is moving away.
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cosmic background radiation
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the electromagnetic radiation left over from the big bang.
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solar nebula
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a stream of electrically charged particles that emanate from the sun's corona.
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planetesimal
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one of the small asteroid-like bodies that formed the building blocks of the planets.
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