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Planet
Arean
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.


Jovian
Image from John M Dollan
A Gas Giant
 
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Appears in Topics
AstronomyPlanetology
 
Development Notes
Text by M. Alan Kazlev
Additional material by Steve Bowers
Initially published on 19 December 2001.

 
 
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