| Terms |
Definitions |
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void
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A volume of space where few, if any, galaxies are located.
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Sa
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spiral galaxy with a large bulge and tightly wound smooth arms
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moons of jupiter
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were used to first measure the speed of light
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planetary nebula
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A small round distribution of gas surrounding a dying star.
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CCD
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An efficient, two-dimensional electronic light detector. Common in digital cameras, they revolutionized astronomical imaging
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Elliptical galaxy
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a round galaxy classified from E0-E7 based on sphericity. little or no interstellar gas and dust. contain few young stars
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disk
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The part of the Milky way that has on-going star formation.
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black hole
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matter so dense that even light cannot escape its gravity.
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interstellar extinction
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The dimming of starlight by intervening dust
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lenticular galaxy
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smaller, lens-shaped galaxy made up of all older stars
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seeing
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A quantity measuring the stability of the Earth's atmosphere.
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electromagnetic radiation
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The family of radiant energy that includes light as a subset.
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molecular clouds
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Large nebula consisting of very cold gas and dust.
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open cluster
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A younger cluster of stars, found in the galaxy disk.
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reflector
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A telescope that uses mirrors to focus light.
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nova
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A star that erratically and explosively brightens and dims.
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nucleus
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The location of a supermassive black hole
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HII region
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A cloud of ionized hydrogen. Formed when young stars heat the surrounding gas.
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extrasolar planet
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A planet orbiting about a distant star.
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primary mirror
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The mirror that gathers the light in a reflector.
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magnification
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The amount an image is enlarged by a telescope.
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300,000 km/sec
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speed of light
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light pollution
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Light scattered through the atmosphere that degrades astronomical images.
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cosmic microwave background
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A faint, remarkably uniform distribution of radiation in space
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self-propagating star formation
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The process responsible for creating the arms of flocculent spiral galaxies
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supernova
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A star that blows itself apart
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metals
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A word used in astronomy to describe all elements besides hydrogen and helium.
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Sb
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spiral galaxy with a moderate bulge, looser arms, moderate lumpiness
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differential rotation
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A term referring to the orbital character of stars near the Sun.
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density wave
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The entity responsible for spiral arms in grand-design spiral galaxies.
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dark matter
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Matter that reveals itself only through its gravitational attraction.
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Doppler shift
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A change in the wavelength of light caused by a motion between the observer and light (or wave) source.
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active optics
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A technique using computer-controlled mirrors to sharpen images distorted by the atmosphere
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Sc
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spiral galaxy with a small bulge, loosely wound arms, and lots of HII regions
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globular cluster
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The oldest grouping of stars, found in the galaxy halo.
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halo
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The oldest part of the Milky Way
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Radio maps
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images that show loop-like images similar to those of the sun
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focal plane
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The area behind a lens where images are resolved.
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nebula
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Latin for "cloud". A word used to describe the collections of gas and dust in the Milky Way and other galaxies
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objective lens
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The lens that gathers the light in a refractor..
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focal length
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The distance between a lens and its focal plane.
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resolving power
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A measure of the ability of a telescope to see fine detai
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secondary mirror
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The mirror that determines the focus configuration of a reflector.
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neutron star
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An object that may remain after a star explodes.
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olaus romer
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first to accurately measure speed of light
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Spiral galaxy
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galaxy shaped like the milky way. containing a halo, disk, and bulge. made of younger population I stars
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photon
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A particle of light
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bulge
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The location in the Milky Way where stars orbit like a solid wheel
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pixel
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An element of a highly efficient, two-dimensional electronic light detector.
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eye piece lens
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The lens in a telescope used to determine the magnification.
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quasar
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The nuclei of very distant galaxies. Likely a manifestation of supermassive black holes.
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radio galaxy
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A galaxy sending out a stream of material from its nucleus.
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light gathering power
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An important quality of telescopes that increases as the square of the primary mirror or objective lens.
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OB associations
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Collections of young, hot stars.
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refractor
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A telescope that uses lenses to focus light.
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rich cluster
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A very dense, highly populated cluster of galaxies.
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supercluster
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The organization of clusters of galaxies into sheets and strings.
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gamma-ray burst
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An energetic event taking place in the early universe.
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poor cluster
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A collection of galaxies like the one the Milky Way belongs to.
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Cassegrain focus
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The telescope configuration that has the focus placed at the back of the primary mirror.
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