See Also

Terrestrial planet

A terrestrial planet or telluric planet is a planet Planet

The International Astronomical Union [i] , the official scientific [i] body for astronomical [i] nomenclature [i] ... 

 that is primarily composed of silicate rocks. The term is derived from the Latin Latin

Latin is an ancient Indo-European language [i] originally spoken in Latium [i], ... 

 word for Earth Earth

Earth is the third planet [i] in the solar system [i] in terms of distance from the Sun [i], and the fi ... 

, "Terra", so an alternate definition would be that these are planets which are, in some notable fashion, "Earth-like". Terrestrial planets are substantially different from gas giant Gas giant

A gas giant is a large planet [i] that is not primarily composed of rock [i] or other solid matter [i] ... 

s, which may not have solid surfaces and are composed mostly of some combination of hydrogen Hydrogen

|- | Triple point [i] || 13.8033 K, 7.042 kPa ... 

, helium Helium

|- | 3He || 0.000137%* || colspan="4" | He is stable [i] with 1 neutron [i] ... 

, and water Water

Water is a taste [i]less, odor [i]less substance that is essential to all known forms of life [i] and i ... 

 existing in various physical states. Terrestrial planets all have roughly the same structure: a central metallic core, mostly iron Iron

Iron is a chemical element [i] with the symbol Fe and atomic number [i] 26. ... 

, with a surrounding silicate mantle Mantle

A Mantle is a piece of clothing, similar to a robe [i] but open on the front side and often sleeveless. ... 

.

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Encyclopedia


A terrestrial planet or telluric planet is a planet Planet

The International Astronomical Union [i] , the official scientific [i] body for astronomical [i] nomenclature [i]... 

 that is primarily composed of silicate rocks. The term is derived from the Latin Latin

Latin is an ancient Indo-European language [i] originally spoken in Latium [i], ... 

 word for Earth Earth

Earth is the third planet [i] in the solar system [i] in terms of distance from the Sun [i], and the fi ... 

, "Terra", so an alternate definition would be that these are planets which are, in some notable fashion, "Earth-like". Terrestrial planets are substantially different from gas giant Gas giant

A gas giant is a large planet [i] that is not primarily composed of rock [i] or other solid matter [i]... 

s, which may not have solid surfaces and are composed mostly of some combination of hydrogen Hydrogen

|-
| Triple point [i] || 13.8033 K, 7.042 kPa
... 

, helium Helium

|-
| 3He || 0.000137%* || colspan="4" | He is stable [i] with 1 neutron [i]
... 

, and water Water

Water is a taste [i]less, odor [i]less substance that is essential to all known forms of life [i] and i ... 

 existing in various physical states. Terrestrial planets all have roughly the same structure: a central metallic core, mostly iron Iron

Iron is a chemical element [i] with the symbol Fe and atomic number [i] 26. ... 

, with a surrounding silicate mantle Mantle

A Mantle is a piece of clothing, similar to a robe [i] but open on the front side and often sleeveless. ... 

. The Moon Moon

The Moon is Earth [i]'s only natural satellite [i]. ... 

 is similar, but lacks an iron core. Terrestrial planets have canyon Canyon

A canyon or gorge is a deep sonoma often carved from the Earth by a river.... 

s, craters Impact crater

An impact crater is a circular or oval depression [i] on a surface, usually referring to a ... 

, mountain Mountain

A mountain is a landform [i] that extends above the surrounding terrain [i] in a limited area. ... 

s, and volcanoes Volcano

A volcano is a geological landform [i] on the surface of the Earth [i] where magma [i] from th ... 

. Terrestrial planets possess secondary atmospheres -- atmospheres generated through internal vulcanism or comet impacts, as opposed to the gas giants, which possess primary atmospheres -- atmospheres captured directly from the original solar nebula Solar nebula

In cosmogony [i], the solar nebula is believed to be a gas [i]eous cloud [i] from which Earth [i]'s solar system formed [i] ... 

.

Earth's solar system Solar System

The Solar System or solar system is the stellar system [i] comprising the Sun [i] and ... 

 has four terrestrial planets: Mercury, Venus Venus

Venus is the second-closest planet [i] to the Sun [i], orbiting it every 224.7 Earth days. ... 

, Earth Earth

Earth is the third planet [i] in the solar system [i] in terms of distance from the Sun [i], and the fi ... 

 and Mars Mars

Mars is the fourth planet [i] from the Sun [i] in our solar system [i] and is named after Mars [i] ... 

. During the formation of the solar system, there were probably many more , but they have all merged with or been destroyed by the four remaining worlds in the solar nebula Solar nebula

In cosmogony [i], the solar nebula is believed to be a gas [i]eous cloud [i] from which Earth [i]'s solar system formed [i] ... 

. Only one terrestrial planet, Earth, is known to have an active hydrosphere Hydrosphere

Hydrosphere in physical geography [i], describes the collective mass of water found on, under, and over ... 

.

Extrasolar terrestrial planets


The majority of planets found outside our solar system Solar System

The Solar System or solar system is the stellar system [i] comprising the Sun [i] and ... 

 to date have been gas giants, simply because gas giants are larger and therefore easier to see or infer from observation. However, a number of extrasolar planets are known or suspected to be terrestrial.

The first terrestrial planets Planet

The International Astronomical Union [i] , the official scientific [i] body for astronomical [i] nomenclature [i]... 

 ever detected outside our solar system were detected by Aleksander Wolszczan Aleksander Wolszczan

Aleksander Wolszczan is a Polish [i] astronomer [i]. ... 

  orbiting the pulsar Pulsar

Pulsars are rotating neutron star [i]s which emit detectable electromagnetic radiation [i] in the form o ... 

 PSR B1257+12 PSR B1257+12

PSR B1257+12 is a pulsar [i] located 980 light year [i]s from Earth.
... 

. Their masses being 0.02, 4.3, and 3.9 Earth Earth

Earth is the third planet [i] in the solar system [i] in terms of distance from the Sun [i], and the fi ... 

 masses. The planets were observed because their transit caused interruptions in the pulsar's radio emissions. Had they not been orbiting around a pulsar, they would never have been found.

When 51 Pegasi b 51 Pegasi b

51 Pegasi b is the first planet discovered around a sun-like star outside of the solar system [i]. ... 

, the first extrasolar planet found around a fusing Stellar nucleosynthesis

Stellar nucleosynthesis is the collective term for the nuclear [i] reactions taking place ... 

 star, was discovered, many astronomers assumed it must be a gigantic terrestrial, as it was assumed no gas giant could exist as close to its star as 51 Pegasi b did. However, subsequent measurements of its diameter confirmed it was a gas giant.

In June 2005, the first planet around a fusing star that is almost certainly terrestrial was found orbiting around the red dwarf Red Dwarf

Red Dwarf is a British [i] science fiction [i] sitcom [i] that ran for eight series, ... 

 star Star

A star is a massive, compact body of plasma [i] in outer space [i] that is held together by its ... 

 Gliese 876 Gliese 876

Gliese 876 is a red dwarf [i] star [i] located approximately 15 light-year [i]s away in the constellation [i]... 

, 15 light years away. That planet has a mass between six and nine times that of earth and an orbital period of just two Earth days.

On 10 August, 2005, Probing Lensing Anomalies NETwork/Robotic Telescope Network  and Optical Gravitational Lensing Experiment  observed the signature of a cold planet designated OGLE-2005-BLG-390Lb OGLE-2005-BLG-390Lb

OGLE-2005-BLG-390Lb is an extrasolar planet [i] orbiting the star [i] OGLE-2005-BLG-390L [i], which is s ... 

, about 5.5 times the mass of Earth, orbiting a star about 21,000 light years away in the constellation Scorpius. The planet revealed its existence through a technique known as gravitational microlensing Gravitational microlensing

Gravitational microlensing is an astronomical [i]
... 

, currently unique in its capability to detect cool planets with masses down to that of Earth.

Already in spring 2005, a microlensing signal indicating the presence of planet OGLE-2005-BLG-169Lb was observed , which is 13 times the mass of Earth and orbiting a star approximately 9,000 light years away. This planet may be either a gas giant or terrestrial. The newly discovered planet orbits its parent star at a distance similar to that of our solar system's asteroid belt Asteroid belt

The asteroid belt is a region of the solar system [i] falling roughly between the planet [i]s Mars [i] ... 

.

Theoretically, there are two types of terrestrial or rocky planets, one dominated by silicon compounds, as Earth is, and another dominated by carbon compounds, like carbonaceous chondrite Carbonaceous chondrite

A carbonaceous chondrite or a C-type chondrite is a type of chondritic [i] meteorite [i] ... 

 asteroids. These are the silicate planet Terrestrial planet

A terrestrial planet or telluric planet is a planet [i] that is primarily composed of silicate [i] ... 

s and carbon planets respectively.

A number of telescopes capable of directly imaging extrasolar terrestrial planets are on the drawing board. These include the Terrestrial Planet Finder Terrestrial Planet Finder

The Terrestrial Planet Finder is a plan by NASA [i] for a telescope [i] system that would be capable of ... 

, Darwin, New Worlds Imager New Worlds Imager

The New Worlds Discoverer is a project funded by NASA Institute for Advanced Concepts [i], headed by Dr. ... 

, and Overwhelmingly Large Telescope Overwhelmingly Large Telescope

The Overwhelmingly Large Telescope is a conceptual design by the European Southern Observatory [i] organ ... 

.

See also


  • Jovian planet Gas giant

    A gas giant is a large planet [i] that is not primarily composed of rock [i] or other solid matter [i]... 

    /Gas giant Gas giant

    A gas giant is a large planet [i] that is not primarily composed of rock [i] or other solid matter [i]... 

     planet
  • Chthonian planet
  • Dwarf planet Dwarf planet

    A dwarf planet is a category of celestial bodies [i] in the solar system [i] as introduced in a resolution [i]... 

  • Planetary habitability Planetary habitability

    Planetary habitability is the measure of an astronomical body's potential to develop and sustain [[life]... 



References

  • Astronomers use gravity lensing to spot homely planets. By Mark Peplow, News @ Nature.com, 25 January 2006.
  • Nature, 439, 437-440.
  • "Closer to Home."
  • National Science Foundation webcast.
  • National Science Foundation grant report.
  • .
  • .
  • .
  • .
  • .

External links

  • SPACE.com: 16 August 2006 2:00 am ET
  • BBC News: Wednesday, 16 August 2006, 13:36 GMT 14:36 UK