Planet

BY LETTER

Planet

Science > Astronomy
Science > Planetology

Image from John M Dollan
An Arean (Mars-like) planet

Spherical object consisting of molten or solid rock and various fractions of volatiles including gases, liquids and ices, larger than planetesimals and smaller than stars or brown dwarfs. Planets are too small to generate energy by nuclear reactions. One of six categories of matter that make up solar systems, nebula, and galaxies, and can be harvested for interplanetary or interstellar development (the other categories are interstellar gas, dust, planetisimals, brown dwarfs, and stars).

Planets are often found orbiting stars, but significant numbers exist as independent objects in deep space. A small number of worlds have developed biospheres of various kinds.

Image from John M Dollan
A Gas Giant

Artificial Planets
Artificial Worlds
CADRS Planetary Classification System, The
Non-Luminary World Classification Scheme
Planetology - Text by M. Alan Kazlev
The study of a planet, moon or asteroid as a whole, including all its component elements, planetary formation, evolution, and taxonomy.

Appears in Topics

Astronomy

Planetology

Development Notes

Text by M. Alan Kazlev
Additional material by Steve Bowers
Initially published on 19 December 2001.

Return to Top