General astronomy

General astronomy

Contributors in General astronomy

General astronomy

The lowest theoretical temperature that is possible to attain. As matter is cooled down, the motion of atoms and molecules gradually comes to a stop. At absolute zero all movement stops. It occurs at ...

Aberration of starlight

Astronomy; General astronomy

Aberration of starlight: The apparent displacement of a star from its real position on the celestial sphere caused by the motion of the Earth in its orbit around the Sun. Aberration was discovered, ...

Absolute magnitude

Astronomy; General astronomy

The apparent magnitude that a star would possess if it were placed (normalized) at a distance of 10 parsecs from the Earth. With the method, absolute magnitude provides a direct comparison of the ...

Absolute cavity radiometer

Astronomy; General astronomy

An instrument used for very accurate measurements of solar irradiance which absorbs radiation on a blackened conical receiver and are electrically self-calibrating. Absolute cavity radiometers ...

Absorber

Astronomy; General astronomy

Any material that can stop ionising radiation. Lead, concrete, and steel all attenuate gamma rays. A thin sheet of paper or metal will stop or absorb alpha particles and most beta particles.

Absolute positioning

Astronomy; General astronomy

A location system in which a position is identified with respect to a well-defined coordinate system such as the commonly geocentric system.

Absorption nebula

Astronomy; General astronomy

A region in space that is made of dust and gas which has no stars to illuminate it from within. As such, these objects are completely dark and obscure any light from stars or emission nebulae which ...