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
Saturn is the sixth planet from the Sun. It is a gas giant, the second-largest planet in the solar system after Jupiter. Saturn has a prominent system of rings, consisting of mostly ice particles ... > more
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
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 ... > more
The Moon is Earth's only natural satellite. The average distance from the Earth to the Moon is 384,399 kilometres (238,854 mi), which is about 30 times the diameter of the Earth. At this distance, it ... > more
Venus is the second-closest planet to the Sun, orbiting it every 224.7 Earth days. It is the brightest object in the night sky, except for the Moon, reaching an apparent magnitude of -4.6. Venus ... > more
A comet is a small body in the solar system that orbits the Sun and (at least occasionally) exhibits a coma (or atmosphere) and/or a tail - both primarily from the effects of solar radiation upon the ... > more