Radience

Stars, Galaxies and 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

binary star

a star system with two stars
binary star Simple Definition

black hole

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

chromosphere

the middle layer of the Sun's atmosphere
chromosphere Simple Definition

constellation

a pattern or shape formed by a group of stars
constellation Simple Definition

corona

the outermost layer of the Sun’s atmosphere
corona Simple Definition

cosmic background radiation

the electromagnetic radiation left over from the big bang
cosmic background radiation Simple Definition

electromagnetic spectrum

all the wavelengths or frequencies of electromagnetic radiation
electromagnetic spectrum Simple Definition

galaxy

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

globular cluster

a large group of old stars densely packed into a roughly spherical shape
globular cluster Simple Definition

Hertzsprung Russell diagram

a graph that plots the surface temperature of stars against their absolute brightness
Hertzsprung Russell diagram Simple Definition

Hubbles law

states that the farther away a galaxy is, the faster it is moving away (as the universe expands)
Hubbles law 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

open cluster

a group of no more than a few thousand stars, all of which are about the same age
open cluster Simple Definition

parallax

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

photosphere

the surface layer of the Sun that gives off light
photosphere Simple Definition

protostar

a very young star, before nuclear reactions begin at its core
protostar Simple Definition

pulsar

a rapidly spinning neutron star that emits radio waves
pulsar Simple Definition

quasar

the very bright center of a distant galaxy
quasar Simple Definition

solar wind

a stream of electrically charged particles released by the Sun’s corona
solar wind Simple Definition

supernova

the bright explosion of a dying supergiant star
supernova Simple Definition

universe

everything that exists, including the stars, planets, and energy
universe 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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