General astronomy

General astronomy

Contributors in General astronomy

General astronomy

A comet's atmosphere (composed of dust and/or various gases) surrounding its nucleus. The coma is rather tenuous (except very close to the nucleus), and stars can be occasionally easily seen through ...

comet

Astronomy; General astronomy

A celestial body orbiting the sun (though some may be ejected from the solar system by planetary perturbations) that displays (at least during a portion of its orbit) some diffuseness and/or a "tail" ...

barycentric dynamical time (TDB)

Astronomy; General astronomy

Differing from TDT only via periodic variations, TDB is used in ephemerides and equations of motion that refer to the barycenter of the solar system.

besselian year

Astronomy; General astronomy

A quantity introduced by F. W. Bessel in the nineteenth century that has been used into the twentieth century. Bessel introduced a system whereby it would be convenient to identify any instant of ...

celestial sphere

Astronomy; General astronomy

An imaginary sphere of great (or infinite) radius that is centered on the earth and is used for practical purposes in astronomical observing. Since stars (other than our own sun!) are very distant ...

astronomical unit (AU)

Astronomy; General astronomy

The average distance from the Earth to the Sun; 1 AU is 149,597,870 kilometers (92,960,116 miles).

charge-coupled device (CCD)

Astronomy; General astronomy

A very sensitive electronic device that is revolutionizing astronomy in the 1990s. CCD cameras are composed of silicon chips that are sensitive to light, changing detected photons of light into ...