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Astronomical unit
The distance between the Earth and the Sun (1AU)
Big Bang theory
A theory of the origin of the universe.It states that the universe came into existence about 13 billion years ago, due to the creation of space-time and the partial conversion of energy into matter.
Cosmic background radiation
The electromagnetic radiation in space that remains following the Big Bang.This radiation cooled as the universe expanded, and is now at an average temperature of 3 degrees above absolute zero (3 K or -270 C)
Galaxy
A vast collections of stars that are held together by gravitational forces.
Light year
The distance light travels in one Earth year.
Nuclear fusion
The process in which nuclei of light elements join together, with the release of large amounts of energy.
Red shift
The shift in frequencies of visible spectral lines towards the red end (low frequency) of the electromagnetic spectrum.A red shift occurs when the object emitting the radiation is moving away from the detector. A red shift in characteristic emission and absorption spectra from distant stars and galaxies indicates that they are moving away from us. This is used as evidence of an expanding universe.
One astronomical unit in kilometres?
1 AU = 150 million kilometres
One light year in kilometres?
1 ly = 9.461 x 10^12 km
Nebula
A cloud of gas and stellar dust
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