Stars, Galaxies and The Universe

Science

absolute magnitude

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

absolute magnitude Simple Definition

apparent magnitude

the brightness of a star as seen from Earth

apparent magnitude Simple Definition

big bang theory

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

big bang theory Simple Definition

black hole

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

black hole Simple Definition

galaxy

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

galaxy Simple Definition

light year

the distance light travels in a year: 9.5 trillion km

light year Simple Definition

main sequence

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

main sequence Simple Definition

nebula

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

nebula Simple Definition

neutron star

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

neutron star Simple Definition

nuclear fusion in the sun

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

nuclear fusion in the sun Simple Definition

parallax

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

parallax Simple Definition

quasar

the very bright center of a distant galaxy

quasar Simple Definition

supernova

the bright explosion of a dying super giant star

supernova Simple Definition

white dwarf

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

white dwarf Simple Definition

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