Gas giant
A gas giant is a large
planet that is not primarily
composed of rock or other
solid matter. Gas giants may
have a rocky or metallic
core—in fact, such a
core is thought to be
required for a gas giant to
... > full story
Extrasolar planet
An extrasolar planet, or
exoplanet, is a planet
beyond the Solar System. As
of 11 November 2006, 209
extrasolar planets have been
discovered.
Known exoplanets are members
of planetary systems that
... > full story
Red giant
A red giant is a large
non-main sequence star of
stellar classification K or
M; so-named because of the
reddish appearance of the
cooler giant stars. As
Earth's sun is of one solar
mass, it is expected to
... > full story
Astrobiology
Astrobiology is the study of
life in space, combining
aspects of astronomy,
biology and geology. It is
focused primarily on the
study of the origin,
distribution and evolution
of life. ... > full story
Browse Reference Articles
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Equatorial bulge
An equatorial bulge is a planetological term which describes a bulge which a planet may have around its equator, distorting it into an oblate spheroid. Because of a planet's equatorial bulge, its ... > more -
Space observatory
A space observatory is any instrument in outer space which is used for observation of distant planets, galaxies, and other outer space objects. A large number of observatories have been launched into ... > more -
Brown dwarf
Brown dwarfs were originally called black dwarfs, a classification for dark substellar objects floating freely in space which were too low in mass to sustain stable hydrogen ... > more -
Asteroid belt
The asteroid belt is a region of the solar system falling roughly between the planets Mars and Jupiter where the greatest concentration of asteroid orbits can be found. Despite popular imagery, the ... > more -
Red supergiant
Red supergiants are supergiant stars of spectral type K-M and a luminosity class of I. They are the largest stars in the universe in terms of physical size, although they are not the most massive. ... > more -
Definition of planet
The definition of "planet" has for some time been the subject of intense debate. Although the word dates back thousands of years, no officially decreed scientific definition of "planet" existed ... > more -
Planetary nebula
A planetary nebula is an astronomical object consisting of a glowing shell of gas and plasma formed by certain types of stars at the end of their lives. They are in fact unrelated to planets; the ... > more -
Planetary habitability
Planetary habitability is the measure of an astronomical body's potential to develop and sustain life. It is generally assumed that any extraterrestrial life that might exist will be based on the ... > more -
Supergiant
Supergiants are the most massive stars. Supergiants can have masses from 10 to 70 solar masses and brightness from 30,000 up to hundreds of thousands times the solar luminosity. They vary greatly in ... > more
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