2M1207b

Planetbox begin
name=2M1207bPlanetbox image

---

caption = Infrared image of 2M1207 (blueish)
and 2M1207b (reddish). The two objects are
separated by less than one arc second in Earth's sky.
Image taken using the ESO's 8.2m Yepun VLT.Planetbox star
star = 2M1207
constell = Centaurus
RA = RA|12|07|33.47SIMBAD link|NAME+2M1207A|NAME 2M1207A, entry, SIMBAD. Accessed on line June 15, 2008.]
DEC = DEC|−39|32|54.0
dist_ly = 172 ± 3
dist_pc = 52.75 ± 1.0 [http://www.cfa.harvard.edu/~emamajek/memo_2m1207.html "The Distance to the 2M1207 System"] , Eric Mamajek, November 8, 2007. Accessed on line June 15, 2008.]
class = M8Planetbox orbit
separation=40.6 ± 1.3Estimated observed projected separation from observed angular separation and estimated distance.]
period_year=~1700
ang_dist = 769 ± 10
position_angle = 125.6 ± 0.7Planetbox character
mass=4⁺⁶_-1 [http://exoplanet.eu/star.php?st=2M1207 Star: 2M1207] , "Extrasolar Planets Encyclopaedia". Accessed on line June 15, 2008.]
radius=1.5
temperature=1600 ± 100The Planetary Mass Companion 2MASS 1207-3932B: Temperature, Mass, and Evidence for an Edge-on Disk, Subhanjoy Mohanty, Ray Jayawardhana, Nuria Huelamo, and Eric Mamajek, "Astrophysical Journal" 657, #2 (March 2007), pp. 1064–1091. bibcode|2007ApJ...657.1064M doi|10.1086/510877.] Planetbox discovery
discoverers=Chauvin et al.
discovery_method=Imaged
discovery_location=European Southern Observatory, Chile
discovery_date=September 2004
discovery_status=PublishedA giant planet candidate near a young brown dwarf. Direct VLT/NACO observations using IR wavefront sensing, G. Chauvin, A.-M. Lagrange, C. Dumas, B. Zuckerman, D. Mouillet, I. Song, J.-L. Beuzit, P. Lowrance, "Astronomy and Astrophysics", 425 (October 2004), pp. L29–L32. bibcode|2004A&A...425L..29C doi|10.1051/0004-6361:200400056.] Planetbox reference
star = 2M1207
planet = b
simbad = NAME+2M1207b

2M1207b is a planetary mass object orbiting the brown dwarf 2M1207, in the constellation Centaurus, approximately 170 light-years from Earth. Notable as one of the first candidate extrasolar planets to be directly observed (by infrared imaging), it was discovered in September 2004 by the Very Large Telescope (VLT) at the Paranal Observatory in Chile by a team from the European Southern Observatory led by Gael Chauvin. It is believed to be from 3 to 10 times the mass of Jupiter and may orbit 2M1207 at a distance roughly as far from the brown dwarf as Pluto is from the Earth's Sun.

The object is a very hot gas giant; the estimated surface temperature is roughly 1600 K (1300 °C or 2400 °F), mostly due to gravitational contraction. Its mass is well below the calculated limit for deuterium fusion in brown dwarfs, which is 13 Jupiter masses. The projected distance between 2M1207b and its primary is around 40 AU (similar to the mean distance between Pluto and the Sun), giving it an estimated orbital period of around 1700 years. Its infrared spectrum indicates the presence of water molecules in its atmosphere. The object is not a likely candidate to support life, either on its surface or on any satellites.

Discovery, identification and properties

2M1207b is around 100 times fainter in the sky than its companion. [Bolometric luminosity, Table 1, Mohanty 2007.] It was first spotted as a "faint reddish speck of light" in 2004 by the VLT. Upon initial observation there was some question as to whether the objects might be merely an optical double, but subsequent observation by the Hubble Space Telescope and the VLT has shown that the objects move together and are therefore presumably a binary system. [http://www.eso.org/public/outreach/press-rel/pr-2005/pr-12-05-p2.html Yes, it is the Image of an Exoplanet: Astronomers Confirm the First Image of a Planet Outside of Our Solar System] , ESO Press Release 12/05, April 30, 2005, European Southern Observatory. Accessed on line June 15, 2008.]

An initial photometric estimate for the distance to 2M1207b was 70 parsecs. In December 2005, American astronomer Eric Mamajek reported a more accurate distance (53 ± 6 parsecs) to 2M1207b using the moving cluster method. [cite journal | url=http://adsabs.harvard.edu/abs/2005ApJ...634.1385M | author=Mamajek| title= A Moving Cluster Distance to the Exoplanet 2M1207b in the TW Hydrae Association | journal= The Astrophysical Journal| volume=634 | year=2005 | pages=1385–1394| doi= 10.1086/468181 ] Recent trigonometric parallax results have confirmed this moving cluster distance, leading to a distance estimate of 53 ± 1 parsecs or 172 ± 3 light years.

Estimates for the mass, size and temperature of 2M1207b are still uncertain. Although spectroscopic evidence is consistent with a mass of 8 ± 2 Jupiter masses and a surface temperature of 1600 ± 100 kelvin, theoretical models for such an object predict a luminosity 10 times greater than observed. Because of this, lower estimates for the mass and temperature have been proposed. Alternatively, 2M1207b might be dimmed by a surrounding disk of dust and gas. As an unlikely possibility, Mamajek and Michael Meyer have suggested that the planet is actually much smaller, but is radiating away heat generated by a recent collision. [An Improbable Solution to the Underluminosity of 2M1207B: A Hot Protoplanet Collision Afterglow, Eric E. Mamajek and Michael R. Meyer, "Astrophysical Journal" 668, #2 (October 2007), pp. L175–L178. bibcode|2007ApJ...668L.175M doi|10.1086/522957.] [cite web | title=Planet collision could explain alien world's heat | date= January 9, 2008| work=NewScientist Space Website | url=http://space.newscientist.com/article/dn13163-planet-collision-could-explain-alien-worlds-heat.html | accessdate=2008-01-11]

Although the mass of 2M1207b is less than that required for deuterium fusion to occur, some 13 times the mass of Jupiter, and the image of 2M1207b has been widely hailed as the first direct image of an extrasolar planet, it may be questioned whether 2M1207b is actually a planet. Some definitions of the term "planet" require a planet to have formed in the same way as the planets in our Solar System did, by secondary accretion in a protoplanetary disk. [E.g., Soter, in What Is a Planet?, "Astronomical Journal" 132, #6 (December 2006), pp. 2513–2519. bibcode|2006AJ....132.2513S doi|10.1086/508861.] With such a definition, if 2M1207b formed by direct gravitational collapse of a gaseous nebula, it would be classed as a sub-brown dwarf rather than a planet. A similar debate exists regarding the identity of GQ Lupi b, also first imaged in 2004. [ [http://www.space.com/scienceastronomy/050430_exoplanet_image.html Fresh Debate over First Photo of Extrasolar Planet] , Robert Roy Britt, space.com, April 30, 2005. Accessed on line June 16, 2008.] On the other hand, the discovery of marginal cases like Cha 110913-773444—a free-floating, planetary-mass object—raises the question of whether distinction by formation is a reliable dividing line between stars/brown dwarfs and planets. [ [http://www.nasa.gov/vision/universe/starsgalaxies/spitzerf-20051129.html A Planet With Planets? Spitzer Finds Cosmic Oddball] , Whitney Clavin, news article, NASA, November 29, 2005. Accessed on line June 16, 2008.] As of 2006, the International Astronomical Union Working Group on Extrasolar Planets described 2M1207b as a "possible planetary-mass companion to a brown dwarf." [ [http://www.dtm.ciw.edu/boss/planets.html Lists of Extrasolar Planets] , IAU Working Group on Extrasolar Planets, August 28, 2006. Accessed on line June 15, 2008.]

ee also

*Extrasolar planet
*Extrasolar moon
*Rogue planet
*Sub-brown dwarf

References

External links

* [http://www.eso.org/outreach/press-rel/pr-2005/pr-12-05-p2.html ESO Press Release 12/05:Yes, it is the Image of an Exoplanet]
* [http://news.bbc.co.uk/2/hi/science/nature/4501323.stm BBC: Planet 'seen' around distant sun]
* [http://space.com/scienceastronomy/aas_exoplanet_050110.html Space.com - Astronomers Confident: Planet Beyond Solar System Has Been Photographed]
* [http://www.space.com/scienceastronomy/planet_photo_040910.html Space.com article on the discovery]
* [http://exoplanet.eu/star.php?st=2M1207 Extrasolar Planets Encyclopedia page on 2M1207b]
* [http://www.sc.eso.org/~gchauvin/Gg222.pdf "A Giant Planet Candidate Near a Young Brown Dwarf" (PDF)] from the European Southern Observatory.
* [http://www.space.com/scienceastronomy/050430_exoplanet_image.html Space.com: Fresh Debate over First Photo of Extrasolar Planet]
* [http://arxiv.org/abs/astro-ph/0507416 "A Moving Cluster Distance to the Exoplanet 2M1207b in the TW Hydrae Association"]
* [http://adsabs.harvard.edu/abs/2007ApJ...657.1064M "The Planetary Mass Companion 2MASS 1207-3932B: Temperature, Mass, and Evidence for an Edge-on Disk"]
* [http://space.newscientist.com/article/dn13163-planet-collision-could-explain-alien-worlds-heat.html "Planet collision could explain alien world's heat"]