Browse Reference Articles
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Dark energy
In physical cosmology, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. Assuming the existence of dark energy is ... > more -
Extraterrestrial life
Extraterrestrial life is life that may exist and originate outside the planet Earth, the only place in the universe currently known by humans to support life. Its existence is currently purely ... > more -
Stellar nucleosynthesis
Stellar nucleosynthesis is the collective term for the nuclear reactions taking place in stars to build the nuclei of the heavier elements. The processes involved began to be understood early in the ... > more -
Solar radiation
Solar radiation is radiant energy emitted by the sun, particularly electromagnetic energy. About half of the radiation is in the visible short-wave part of the electromagnetic spectrum. The other ... > more -
Globular cluster
A globular cluster is a spherical collection of stars that orbits a galactic core as a satellite. Globular clusters are very tightly bound by gravity, which gives them their spherical shapes and ... > more -
Gravitation
Gravity is a force of attraction that acts between bodies that have mass. Gravity is the reason for the very existence of the earth, the sun and other celestial bodies; without it matter would not ... > more -
Solar System
The Solar System consists of the Sun and the other celestial objects gravitationally bound to it: the eight planets, their 165 known moons, three dwarf planets (Ceres, Pluto, and Eris and their four ... > more
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