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Planetary System

 
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A planetary system consists of the various non-stellar objects orbit
ORBit

ORBit is a Common Object Request Broker Architecture 2.4 compliant Object Request Broker . It features mature C , C++ and Python bindings, and less developed bindings for Perl, Lisp , Pascal , Ruby , and Tcl....
ing a star
Star

A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
 such as planet
Planet

A planet , as 2006 definition of planet by the International Astronomical Union , is a celestial body orbiting a star or Stellar evolution#Stellar remnants that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared the neighbourhood of planetesimals....
s, moon
Natural satellite

A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called the primary. Technically, the term natural satellite could refer to a planet orbiting a star, or a dwarf galaxy orbiting a major galaxy, but it is normally synonymous with moon and used to identify non-artificial satellites...
s, asteroid
Asteroid

Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, smaller than planets but larger than meteoroids....
s, meteoroid
Meteoroid

A meteoroid is a small sand to boulder sized particle of debris in the Solar System. The visible path of a meteoroid that enters Earth Earth's atmosphere is called a meteor, or commonly a "shooting star" or "falling star"....
s, comet
Comet

A comet is a Small Solar System body that orbits the Sun and, when close enough to the Sun, exhibits a visible coma or a tail?both primarily from the effects of solar radiation upon the Comet nucleus....
s, and cosmic dust
Cosmic dust

Cosmic dust is a type of dust composed of particles in space which are a few molecules to 0.1 mm in size. Cosmic dust can be further distinguished by its astronomical location; for example: intergalactic dust, interstellar dust , interplanetary dust and circumplanetary dust ....
. The Sun
Sun

The Sun , a G V star, is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 98.6% of the Solar System's mass....
 together with its planetary system, which includes Earth
Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
, is known as the Solar System
Solar System

The Solar System consists of the Sun and those Astronomical object bound to it by gravity: the eight planets and five dwarf planets, their 173 known Natural satellite, and billions of Small Solar System body....
.

etary systems are generally believed to form as part of the same process which results in star formation
Star formation

Star formation is the process by which dense parts of molecular clouds collapse into a ball of Plasma to form a star. As a branch of astronomy star formation includes the study of the interstellar medium and giant molecular clouds as precursors to the star formation process and the study of young stellar objects and planet formation as its i...
.






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A planetary system consists of the various non-stellar objects orbit
ORBit

ORBit is a Common Object Request Broker Architecture 2.4 compliant Object Request Broker . It features mature C , C++ and Python bindings, and less developed bindings for Perl, Lisp , Pascal , Ruby , and Tcl....
ing a star
Star

A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
 such as planet
Planet

A planet , as 2006 definition of planet by the International Astronomical Union , is a celestial body orbiting a star or Stellar evolution#Stellar remnants that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared the neighbourhood of planetesimals....
s, moon
Natural satellite

A natural satellite or moon is a celestial body that orbits a planet or smaller body, which is called the primary. Technically, the term natural satellite could refer to a planet orbiting a star, or a dwarf galaxy orbiting a major galaxy, but it is normally synonymous with moon and used to identify non-artificial satellites...
s, asteroid
Asteroid

Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, smaller than planets but larger than meteoroids....
s, meteoroid
Meteoroid

A meteoroid is a small sand to boulder sized particle of debris in the Solar System. The visible path of a meteoroid that enters Earth Earth's atmosphere is called a meteor, or commonly a "shooting star" or "falling star"....
s, comet
Comet

A comet is a Small Solar System body that orbits the Sun and, when close enough to the Sun, exhibits a visible coma or a tail?both primarily from the effects of solar radiation upon the Comet nucleus....
s, and cosmic dust
Cosmic dust

Cosmic dust is a type of dust composed of particles in space which are a few molecules to 0.1 mm in size. Cosmic dust can be further distinguished by its astronomical location; for example: intergalactic dust, interstellar dust , interplanetary dust and circumplanetary dust ....
. The Sun
Sun

The Sun , a G V star, is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 98.6% of the Solar System's mass....
 together with its planetary system, which includes Earth
Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
, is known as the Solar System
Solar System

The Solar System consists of the Sun and those Astronomical object bound to it by gravity: the eight planets and five dwarf planets, their 173 known Natural satellite, and billions of Small Solar System body....
.

Origin and evolution

Protoplanetary Disk
Planetary systems are generally believed to form as part of the same process which results in star formation
Star formation

Star formation is the process by which dense parts of molecular clouds collapse into a ball of Plasma to form a star. As a branch of astronomy star formation includes the study of the interstellar medium and giant molecular clouds as precursors to the star formation process and the study of young stellar objects and planet formation as its i...
. Some early theories involved another star passing extremely close to the Sun, 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 a protoplanetary disk
Protoplanetary disk

A protoplanetary disk is a rotating circumstellar disk of dense gas surrounding a young newly formed star, a T Tauri star or Herbig Ae/Be stars....
 forms by gravitational collapse of a molecular cloud
Molecular cloud

A molecular cloud, sometimes called a stellar nursery if star formation is occurring within, is a type of interstellar cloud whose density and size permits the formation of molecules, most commonly molecular hydrogen ....
 and then evolves into a planetary system by collisions and gravitational capture.

Some planetary systems may form differently, however. Planets orbiting pulsar
Pulsar

Pulsars are highly magnetized, rotating neutron stars that emit a beam of electromagnetic radiation. The observed periods of their pulses range from 1.4 milliseconds to 8.5 seconds....
s—star
Star

A star is a massive, luminous ball of Plasma that is held together by its own gravity. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth....
s which emit periodic bursts of electromagnetic radiation
Electromagnetic radiation

Electromagnetic radiation takes the form of wave propagation waves in a vacuum or in matter. EM radiation has an electric field and magnetic field component which oscillate in phase perpendicular to each other and to the direction of energy Wave propagation....
—have been discovered by the slight variations they cause in the timing of these bursts. Pulsars are formed in violent supernova
Supernova

A supernova is a Astronomy#Stellar astronomy explosion. Supernovae are extremely luminous and cause a burst of radiation that often briefly outshines an entire galaxy, before fading from view over several weeks or months....
 explosions, and a normal planetary system could not possibly survive such a blast—planets would either evaporate, be pushed off of their orbits by the masses of gas from the exploding star, 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 surrounding pulsars.

List of planetary systems

Extrasolar Planet Nasa2
* Solar System
Solar System

The Solar System consists of the Sun and those Astronomical object bound to it by gravity: the eight planets and five dwarf planets, their 173 known Natural satellite, and billions of Small Solar System body....
 – The Sun
Sun

The Sun , a G V star, is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 98.6% of the Solar System's mass....
 and its planetary system, the first such system discovered
  • PSR B1257+12
    PSR B1257+12

    PSR B1257+12, sometimes abbreviated as PSR 1257+12, is a pulsar located 980 light-years from the Sun. As of 2007, it is confirmed that three extrasolar planets pulsar planet....
     – the first extrasolar planetary system discovered, the first pulsar
    Pulsar

    Pulsars are highly magnetized, rotating neutron stars that emit a beam of electromagnetic radiation. The observed periods of their pulses range from 1.4 milliseconds to 8.5 seconds....
     planetary system discovered, the first multi exoplanet system discovered
  • Upsilon Andromedae
    Upsilon Andromedae

    Upsilon Andromedae is a binary star located approximately 44 light-years away from Earth in the constellation Andromeda . The primary star is a yellow dwarf star that is somewhat younger than the Sun....
     – the first multiplanet extrasolar planetary system discovered around a main sequence
    Main sequence

    The main sequence is a continuous and distinctive band of stars that appear on plots of stellar Color index versus brightness. These color-absolute magnitude plots are known as Hertzsprung-Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell....
     star, found to be so in April 1999
  • PSR B1620-26
    PSR B1620-26

    PSR B1620-26 is a binary star system approximately 12,400 light-years away in the constellation of Scorpius. The system is comprised of a pulsar and a white dwarf....
     – the first multistar planetary system discovered.
  • 55 Cancri
    55 Cancri

    55 Cancri , also cataloged Rho1 Cancri or abbreviated 55 Cnc, is a binary star approximately 41 light-years away from Earth in the constellation of Cancer ....
     – the largest extrasolar planetary system discovered (5 known planets as of November 6, 2007, along with a distant stellar companion.)
  • Gliese 876
    Gliese 876

    Gliese 876 is a red dwarf star approximately 15 light-years away from Earth in the constellation of Aquarius . As of 2008, it has been confirmed that three extrasolar planets orbit the star....
     – the first system around a red dwarf
    Red Dwarf

    Red Dwarf is a United Kingdom science fiction television situation comedy Media franchise, primarily comprising eight series of a television sitcom that ran on BBC Two between 1988 and 1999 and gained a cult following....
     star and the first discovered to be in an orbital resonance
    Orbital resonance

    In celestial mechanics, an orbital resonance occurs when two orbiting bodies exert a regular, periodic gravitational influence on each other, usually due to their orbital periods being related by a ratio of two small integers....
  • HD 69830
    HD 69830

    HD 69830 is an orange dwarf star approximately 41 light-years away in the constellation of Puppis. In 2005, the Spitzer Space Telescope discovered an asteroid belt orbiting the star....
     – found to have three Neptune-mass planets and an asteroid belt, all within 1 AU
  • 2M1207
    2M1207

    2M1207, 2M1207A or 2MASSW J1207334-393254 is a brown dwarf located in the constellation Centaurus; a companion object, 2M1207b, may be the first extrasolar planetary mass object companion to be directly imaged, and is the first discovered orbiting a brown dwarf....
     – the first imaged system and the first brown dwarf
    Brown dwarf

    Brown dwarfs are sub-star objects with a mass below that necessary to maintain hydrogen-burning nuclear fusion reactions in their cores, as do stars on the main sequence, but which have fully convective surfaces and interiors, with no chemical differentiation by depth....
     system with a planet discovered
  • Gliese 581
    Gliese 581

    Gliese 581 is a red dwarf star with stellar classification M3V, located 20.3 light years away from Earth. Its mass is estimated to be approximately a third that of the Sun, and it is the 87th closest known star system to the Sun....
     - first extrasolar system discovered with a planet located within the habitable zone
    Habitable zone

    The habitable zone in astronomy is a region of space where stellar conditions are favorable for life as it is found on Earth. There are two regions that must be favorable, one within a planetary system and the other within the galaxy....
     (Gliese 581 c
    Gliese 581 c

    Gliese 581 c is an List of unconfirmed exoplanets "super-earth", a large terrestrial planet extrasolar planet orbiting the red dwarf star Gliese 581....
    )
  • Mu Arae
    Mu Arae

    Mu Arae , often catalogued as HD 160691, is a G V star star approximately 50 light-years away from Earth in the constellation of Ara . The star has a planetary system with four known planets, three of them with masses comparable to that of Jupiter....
     - The system's innermost planet was the first "hot Neptune" to be discovered
  • HD 188753
    HD 188753

    HD 188753 is a triple star system approximately 149 light-years away in the constellation of Cygnus . In 2005, an extrasolar planet was announced to be orbiting the primary star in the system....
     - The first triple star planetary system discovered
  • HD 37124
    HD 37124

    HD 37124 is a yellow dwarf star approximately 108 light-years away in the constellation of Taurus . As of 2005, three extrasolar planets have been confirmed to orbit the star....
  • HD 12661
    HD 12661

    |- bgcolor="#FFFAFA"HD 12661 is a yellow star in the constellation of Aries . It has two known extrasolar planets. It is 121 light years from Earth and is one and a half times larger than our Sun....
  • HD 73526
    HD 73526

    HD 73526 is a yellow dwarf star about 323 light-years away in the constellation Vela ....
  • 47 Ursae Majoris
    47 Ursae Majoris

    47 Ursae Majoris, often abbreviated as 47 UMa, is a solar twin, yellow dwarf star approximately 46 light-years away from Earth in the constellation of Ursa Major....
  • Epsilon Eridani
    Epsilon Eridani

    Epsilon Eridani is a main sequence star of stellar classification K2. Only 10.5 light years away, it is the closest star in the constellation Eridanus , as well as the third List of nearest stars visible to the naked eye....
  • 14 Herculis
    14 Herculis

    14 Herculis is an orange dwarf star approximately 59 light-years away in the constellation Hercules . Because of its apparent magnitude, the star cannot be seen with the naked eye....
  • UX Tau A


See also

  • Extrasolar planet
    Extrasolar planet

    An extrasolar planet, or exoplanet, is a planet beyond the Solar System, orbiting a star other than the Sun. As of February 2009, 342 exoplanets are listed in the Extrasolar Planets Encyclopaedia....
  • List of stars with confirmed extrasolar planets
    List of stars with confirmed extrasolar planets

    Extrasolar planets were first confirmed to be orbiting the pulsars PSR B1257+12 and PSR B1620-26. These discoveries were announced in 1992 and 1993 respectively....
  • Stellar nursery
  • Stars and planetary systems in fiction