Stars, Galaxies and The Universe

Science

absolute magnitude

the brightness of a star as seen from a distance of 10 parsecs

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apparent magnitude

the brightness of a star as seen from Earth

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big bang theory

states that the universe began with a huge explosion 13.8 billion years ago

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black hole

a region in space with gravity so strong that no matter or light can escape it

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galaxy

a massive system of stars, gases, and dust held together by gravity

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light year

the distance light travels in a year: 9.5 trillion km

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main sequence

the distinct diagonal band on an H-R diagram that includes 90% of all stars

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nebula

a huge cloud of gas and dust in space, where new stars form

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neutron star

a dense core composed mainly of neutrons, left behind after a supernova explosion

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nuclear fusion in the sun

the process by which hydrogen atoms join together to form helium, inside the sun

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parallax

the apparent change in position of an object when viewed from different places

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quasar

the very bright center of a distant galaxy

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supernova

the bright explosion of a dying super giant star

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white dwarf

the hot dense core of a star left behind when its outer layers have escaped into space

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