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galactic disk
the disk of a spiral galaxy
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galactic nucleus
the central region of a galaxy; often contains a high density of stars and gas, and a supermassive black hole
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galactic plane
the projection of the Milky Way’s disk on the sky.
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galaxy
an enormous gravitationally bound assemblage of millions or billions of stars
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galaxy cluster
a gravitationally bound assemblage of dozens to thousands of galaxies
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gamma rays
the form of light (electromagnetic radiation) with the shortest wavelength and the most energy
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gamma-ray burst
a short, intense burst of high-energy radiation emanating from the distant universe
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gas giant
a large planet made primarily of gas, such as Jupiter, Saturn, Uranus, and Neptune
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general relativity
the theory of relativity governing accelerated motion that describes gravity as a curvature of space-time
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german equatorial mount
a mount in which the declination axis sits on top of the polar axis, with the telescope on one end of the declination axis and a counterweight on the other
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giant molecular cloud
interstellar clouds of cold gas and dust that contain tens or hundreds of thousands of solar masses
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gibbous
the phase of the moon between first quarter and last quarter, when the moon appears more than half illuminated
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globular cluster
a roughly spherical congregation of hundreds of thousands of stars; most globular clusters consist of old stars and exist in a galaxy’s halo
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gravitational lens
a massive object which magnifies or distorts the light from a more distant object along the same line of sight
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gravitational lensing
the distortion or amplification of an object’s light due to the presence of a massive object in the light path
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gravitational waves
weak, wavelike disturbances which represent the radiation related to the gravitational force; produced when massive bodies are accelerated or otherwise disturbed
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gravity
the attractive force that all objects exert on one another; the greater an object’s mass, the stronger its gravitational pull
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gravity waves
weak, wavelike disturbances which represent the radiation related to the gravitational force; produced when massive bodies are accelerated or otherwise disturbed
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