A planetary system consists of at least one star and various orbiting objects (such as asteroids, comets, moons, and planets). Our own planetary system which contains the Earth and Sun is called the Solar System. The Pleiades star cluster A star is any massive gaseous body in outer space just like the Sun. ... For other meanings of the term orbit, see orbit (disambiguation) In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ... An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... Comet Hale-Bopp, showing a white dust tail and blue gas tail (February 1997) Comet (disambiguation). ... The common noun moon (not capitalized) is used to mean any natural satellite of the other planets. ... A planet (from the Greek πλανήτης, planētēs or wanderers) is a body of considerable mass that orbits a star and that produces no energy through nuclear fusion. ... Earth, also known as the Earth or Terra, is the third planet outward from the Sun. ... A Sun is the star at the centre of a solar system. ... Mosaic of the planets of the solar system, excluding Pluto, and including Earths Moon. ...

Origin and evolution of planetary systems

Planetary systems around sun-like stars are generally believed to form as part of the same process which results in star formation. Some early theories involved another star passing extremely close to the sun, and drawing material out from it which then coalesced to form the planets. However, the probability of such a near collision is now known to be far too low to make this a viable model. Accepted theories today argue that planetary systems form from a solar nebula. Star formation is the process by which gas in molecular clouds gets transformed into stars. ... In cosmogony, the solar nebula is the gaseous cloud (or accretion disc) from which our solar system is believed to have formed. ...

Some planetary systems are very unlike our own, however: planetary systems around pulsars have been inferred from slight variations in the period of the pulses of electromagnetic radiation. Pulsars are formed in violent supernova explosions, and a normal planetary system could not possibly survive such a blast - planets would either evaporate, or the sudden loss of most of the mass of the central star would see them escape the gravitational hold of the star. One theory is that existing stellar companions were almost entirely evaporated by the supernova blast, leaving behind planet-sized bodies. Alternatively, planets may somehow form in the accretion disk which surrounds pulsars. Composite Optical/X-ray image of the Crab Nebula pulsar, showing surrounding nebular gases stirred by the pulsars magnetic field and radiation. ... Remnant of Keplers Supernova, SN 1604. ... An accretion disc (or accretion disk) is a structure formed by material falling into a gravitational source. ...

Significant planetary systems

• Solar System - our planetary system, the first planetary system discovered, the first multiplanet planetary system discovered
• PSR 1257+12 - the first extrasolar planetary system discovered, the first pulsar planetary system discovered, the first multi exoplanet system discoverd, the first multi planet system with a pulsar discovered
• Upsilon Andromedae - the first multiplanet extrasolar planetary system discovered around a main sequence star, found to be so in April 1999
• PSR B1620-26 - the first multistar planetary system discovered
• 55 Cancri - the largest extra solar planetary system discovered (4 planets, as of August 2004)
• Gliese 876 - the first system around a red dwarf star and the first discovered to be in an orbital resonance

Mosaic of the planets of the solar system, excluding Pluto, and including Earths Moon. ... The title given to this article is incorrect due to technical limitations. ... Composite Optical/X-ray image of the Crab Nebula pulsar, showing surrounding nebular gases stirred by the pulsars magnetic field and radiation. ... Pulsar planets are planets that are found orbiting pulsars. ... Upsilon Andromedae (or υ Andromedae) is a star, approximately 44 light-years from Earth, and approximately 3 billion years old, two thirds the age of our Sun. ... Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ... PSR B1620-26 is also called PSR J1623-2631 (or or ) Contents // Categories: Astronomy stubs | Star systems | Planetary systems | Binary stars ... 55 Cancri is a G type star 41 light-years or 12. ... 2004 : January - February - March - April - May - June - July - August - September - October - November - December See also: August 2004 in sports Deaths in August 2004 • 30 Fred Whipple • 26 Laura Branigan • 24 Elisabeth Kübler_Ross • 18 Elmer Bernstein • 15 Amarsinh Chaudhary • 14 Czesław Miłosz • 13 Julia Child • 8 Robert Bootzin • 8 Fay Wray... Gliese 876 is a red dwarf star (spectral type M4V) 15 light years from Earth in the constellation of Aquarius. ... This article is about red dwarfs, the type of star. ... Orbital Resonance is also the title of a science fiction novel by John Barnes. ...

See also

• Extrasolar planet
• List of stars with confirmed extrasolar planets
• List of stars with multiple exoplanets