General astronomy

General astronomy

Contributors in General astronomy

General astronomy

The physical process whereby a gamma-ray photon, usually through an interaction with the electromagnetic field of a nucleus, produces an electron and an anti-electron (positron). The original photon ...

semimajor axis

Astronomy; General astronomy

The semimajor axis of an ellipse (e.g. a planetary orbit) is half the length of the major axis, which is the line segment passing through the foci of the ellipse with endpoints on the ellipse itself. ...

albedo

Astronomy; General astronomy

the fraction of light reflected from an object. Specified as a decimal fraction from 0 (total absorption) to 1 (total reflection).

altitude

Astronomy; General astronomy

position on the celestial sphere that is the number of degrees an object is above the nearest horizon. Varies from 0° at horizon to 90° at zenith. Vertical position of an object.

angular momentum

Astronomy; General astronomy

a measure of the amount of spin or orbital motion an object has. It is proportional to the mass of the object multiplied by its radius multiplied by its spin or orbital speed.

angular size

Astronomy; General astronomy

the apparent size of an object measured by the angle between two lines of sight along each side of an object. An object's actual linear diameter can be found from the angular size if the distance is ...

Kelvin scale

Astronomy; General astronomy

a temperature scale that directly scales with the random motion energy of a substance, such that 0 Kelvin is at absolute zero (state where all random motion ceases) and higher temperatures have ...