2M1207b is a planetary mass object
orbitingIn physics, an orbit is the gravitationally curved path of one object around a point or another body, for example the gravitational orbit of a planet around a star....
the
brown dwarfBrown dwarfs are sub-stellar 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...
2M12072M1207, 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 companion to be directly imaged, and is the first discovered orbiting a brown dwarf.2M1207 was discovered during the course of...
, in the constellation
CentaurusCentaurus is a bright constellation in the southern sky. One of the largest constellations in the sky, Centaurus was included among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations.-Stars:...
, approximately 170
light-yearAs defined by the International Astronomical Union , a light-year is the distance that light travels in a vacuum in one Julian year.The speed of light is 299,792,458 metres per second...
s from Earth. Notable as one of the first candidate extrasolar planets to be directly observed (by
infraredInfrared radiation is electromagnetic radiation whose wavelength is longer than that of visible light , but shorter than that of terahertz radiation and microwaves...
imaging), it was discovered in September 2004 by the
Very Large TelescopeThe Very Large Telescope is a very large telescope made up of four separate optical telescopes organized in an array formation, built and operated by the European Southern Observatory at the Paranal Observatory on Cerro Paranal, a 2,635 m high mountain...
(VLT) at the
Paranal ObservatoryParanal Observatory is an astronomical observatory located on Cerro Paranal at 2,635 mts. altitude and operated by the European Southern Observatory. The Very Large Telescope is the largest telescope on Paranal, actually composed of four separate 8.2 m telescopes...
in
ChileChile, officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
by a team from the
European Southern ObservatoryThe European Southern Observatory , is an intergovernmental research organization for astronomy, composed and supported by fourteen countries from Europe...
led by Gaël Chauvin. It is believed to be from 3 to 10 times the mass of
JupiterJupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with a mass slightly less than one-thousandth that of the Sun but is two and a half times the mass of all of the other planets in our Solar System combined. Jupiter is classified as a gas...
and may orbit 2M1207 at a distance roughly as far from the brown dwarf as
PlutoPluto, formal designation 134340 Pluto, is the second-largest known dwarf planet in the Solar System and the tenth-largest body observed directly orbiting the Sun...
is from the Earth's
SunThe Sun is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass....
.
The object is a very hot
gas giantA gas giant is a large planet that is not primarily composed of rock or other solid matter. There are four gas giants in our Solar System: Jupiter, Saturn, Uranus, and Neptune...
; the estimated surface
temperatureIn physics, temperature is a physical property of a system that underlies the common notions of hot and cold; something that feels hotter generally has the higher temperature. Temperature is one of the principal parameters of thermodynamics...
is roughly 1600
KThe kelvin is a unit increment of temperature and is one of the seven SI base units. The Kelvin scale is a thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero kelvin...
(1300 °
CCelsius is a temperature scale that is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
or 2400 °
FFahrenheit is the temperature scale proposed in 1724 by, and named after, the physicist Daniel Gabriel Fahrenheit . Today, the scale has been replaced by the Celsius scale in most countries; it is still in use for non-scientific purposes in the United States and a few other nations, such as...
), mostly due to gravitational contraction.
2M1207b is a planetary mass object
orbitingIn physics, an orbit is the gravitationally curved path of one object around a point or another body, for example the gravitational orbit of a planet around a star....
the
brown dwarfBrown dwarfs are sub-stellar 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...
2M12072M1207, 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 companion to be directly imaged, and is the first discovered orbiting a brown dwarf.2M1207 was discovered during the course of...
, in the constellation
CentaurusCentaurus is a bright constellation in the southern sky. One of the largest constellations in the sky, Centaurus was included among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations.-Stars:...
, approximately 170
light-yearAs defined by the International Astronomical Union , a light-year is the distance that light travels in a vacuum in one Julian year.The speed of light is 299,792,458 metres per second...
s from Earth. Notable as one of the first candidate extrasolar planets to be directly observed (by
infraredInfrared radiation is electromagnetic radiation whose wavelength is longer than that of visible light , but shorter than that of terahertz radiation and microwaves...
imaging), it was discovered in September 2004 by the
Very Large TelescopeThe Very Large Telescope is a very large telescope made up of four separate optical telescopes organized in an array formation, built and operated by the European Southern Observatory at the Paranal Observatory on Cerro Paranal, a 2,635 m high mountain...
(VLT) at the
Paranal ObservatoryParanal Observatory is an astronomical observatory located on Cerro Paranal at 2,635 mts. altitude and operated by the European Southern Observatory. The Very Large Telescope is the largest telescope on Paranal, actually composed of four separate 8.2 m telescopes...
in
ChileChile, officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
by a team from the
European Southern ObservatoryThe European Southern Observatory , is an intergovernmental research organization for astronomy, composed and supported by fourteen countries from Europe...
led by Gaël Chauvin. It is believed to be from 3 to 10 times the mass of
JupiterJupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with a mass slightly less than one-thousandth that of the Sun but is two and a half times the mass of all of the other planets in our Solar System combined. Jupiter is classified as a gas...
and may orbit 2M1207 at a distance roughly as far from the brown dwarf as
PlutoPluto, formal designation 134340 Pluto, is the second-largest known dwarf planet in the Solar System and the tenth-largest body observed directly orbiting the Sun...
is from the Earth's
SunThe Sun is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass....
.
The object is a very hot
gas giantA gas giant is a large planet that is not primarily composed of rock or other solid matter. There are four gas giants in our Solar System: Jupiter, Saturn, Uranus, and Neptune...
; the estimated surface
temperatureIn physics, temperature is a physical property of a system that underlies the common notions of hot and cold; something that feels hotter generally has the higher temperature. Temperature is one of the principal parameters of thermodynamics...
is roughly 1600
KThe kelvin is a unit increment of temperature and is one of the seven SI base units. The Kelvin scale is a thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero kelvin...
(1300 °
CCelsius is a temperature scale that is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
or 2400 °
FFahrenheit is the temperature scale proposed in 1724 by, and named after, the physicist Daniel Gabriel Fahrenheit . Today, the scale has been replaced by the Celsius scale in most countries; it is still in use for non-scientific purposes in the United States and a few other nations, such as...
), mostly due to gravitational contraction. Its
massIn physics, mass commonly refers to any of three properties of matter, which have been shown experimentally to be equivalent: inertial mass, active gravitational mass and passive gravitational mass...
is well below the calculated limit for
deuteriumDeuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of Earth of approximately one atom in of hydrogen...
fusionIn nuclear physics and nuclear chemistry, nuclear fusion is the process by which multiple like-charged atomic nuclei join together to form a heavier nucleus...
in brown dwarfs, which is 13
Jupiter massJupiter mass , is the unit of mass equal to the total mass of the planet Jupiter . Jupiter mass is used to describe masses of the gas giants, such as the outer planets and extrasolar planets...
es. The projected
distanceDistance is a numerical description of how far apart objects are. In physics or everyday discussion, distance may refer to a physical length, a period of time, or an estimation based on other criteria . In mathematics, a distance function or metric is a generalization of the concept of physical...
between 2M1207b and its primary is around 40
AUAn astronomical unit is a unit of length roughly equal to the mean distance between the Earth and the Sun. It is approximately 150 million kilometres ....
(similar to the mean distance between
PlutoPluto, formal designation 134340 Pluto, is the second-largest known dwarf planet in the Solar System and the tenth-largest body observed directly orbiting the Sun...
and the
SunThe Sun is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass....
). Its infrared spectrum indicates the presence of
waterWater is an ubiquitous chemical substance that is composed of hydrogen and oxygen and is essential for all known forms of life.In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71%...
molecules in its atmosphere. The object is not a likely candidate to support
lifeLife is a characteristic that distinguishes objects that have self-sustaining biological processes from those that do not—either because such functions have ceased , or else because they lack such functions and are classified as "inanimate."In biology, the science of living organisms, "life"...
, either on its surface or on any
satelliteIn the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavor. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
s.
Discovery, identification and properties
2M1207b is around 100 times fainter in the sky than its companion. It was first spotted as a "faint reddish speck of light" in 2004 by the
VLTThe Very Large Telescope is a very large telescope made up of four separate optical telescopes organized in an array formation, built and operated by the European Southern Observatory at the Paranal Observatory on Cerro Paranal, a 2,635 m high mountain...
. 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 TelescopeThe Hubble Space Telescope is a space telescope that was carried into orbit by the space shuttle in April 1990. It is named after the American astronomer Edwin Hubble. Although not the first space telescope, the Hubble is one of the largest and most versatile, and is well-known as both a vital...
and the VLT has shown that the objects move together and are therefore presumably a
binary systemA binary system is an astronomical term referring to two objects in space which are so close that their gravitational interaction causes them to orbit about a common center of mass. Some definitions A binary system is an astronomical term referring to two objects in space (usually stars, but also...
.
An initial
photometricPhotometry can refer to:*Photometry , the science of measurement of visible light in terms of its perceived brightness to human vision*Photometry , the measurement of the flux or intensity of an astronomical object's electromagnetic radiation...
estimate for the distance to 2M1207b was 70
parsecThe parsec is a unit of length, equal to just under 31 million million kilometres , or about 3.26 light-years. The parsec measurement unit is used in astronomy and is defined as the length of the adjacent side of an imaginary right triangle in space...
s. In December 2005, American astronomer Eric Mamajek reported a more accurate distance (53 ± 6 parsecs) to 2M1207b using the
moving cluster methodIn astrometry, the moving cluster method and the closely related convergent point method are means, primarily of historical interest, for determining the distance to star clusters. They were used on several nearby clusters in the first half of the 1900s to determine distance...
. Recent trigonometric
parallaxParallax is an apparent displacement or difference of orientation of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines...
results have confirmed this moving cluster distance, leading to a distance estimate of 52.75 parsecs or 172 ± 3
light yearsLight Years is the seventh album by Australian singer Kylie Minogue and was released in 2000. It reached number two in the United Kingdom and one on the Australian album charts and number two in New Zealand being certified platinum there . Light Years is largely seen as Minogue's "comeback" album...
.
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
kelvinThe kelvin is a unit increment of temperature and is one of the seven SI base units. The Kelvin scale is a thermodynamic temperature scale where absolute zero, the theoretical absence of all thermal energy, is zero 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.
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 SystemThe Solar System consists of the Sun and those celestial objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago...
did, by secondary accretion in a
protoplanetary diskA protoplanetary disk is a rotating circumstellar disk of dense gas surrounding a young newly formed star, a T Tauri star or Herbig star...
. With such a definition, if 2M1207b formed by direct
gravitational collapseGravitational collapse in astronomy is the inward fall of a massive body under the influence of gravity. It occurs when all other forces fail to supply a sufficiently high pressure to counterbalance gravity and keep the massive body in hydrostatic equilibrium.Gravitational collapse is at the heart...
of a gaseous
nebulaA nebula is an interstellar cloud of dust, hydrogen gas, helium gas and plasma...
, it would be classed as a
sub-brown dwarfA sub-brown dwarf is a planetary-mass object whose mass is smaller than the low-mass cut-off for brown dwarfs . Unlike proper brown dwarfs, they are not massive enough to fuse deuterium. Sub-brown dwarfs are formed in the manner of stars, through the collapse of a gas cloud, and not through...
rather than a planet. A similar debate exists regarding the identity of
GQ Lupi bGQ Lupi b is a possible extrasolar planet orbiting the star GQ Lupi. Its discovery was announced in April 2005. Along with 2M1207b, this was one of the first extrasolar planet candidates to be directly imaged...
, also first imaged in 2004. On the other hand, the discovery of marginal cases like
Cha 110913-773444Cha 110913-773444 is an astronomical object surrounded by what appears to be a protoplanetary disk. There is no consensus yet among astronomers whether to classify the object as a sub-brown dwarf or a rogue planet...
—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. As of 2006, the
International Astronomical UnionThe International Astronomical Union is a collection of professional astronomers, at the Ph.D. level and beyond, active in professional research and education in astronomy...
Working Group on Extrasolar Planets described 2M1207b as a "possible planetary-mass companion to a brown dwarf."
See also
- Extrasolar planet
An extrasolar planet, or exoplanet, is a planet beyond our solar system, orbiting a star other than our Sun. , 403 exoplanets are listed in the Extrasolar Planets Encyclopaedia. The vast majority have been detected through radial velocity observations and other indirect methods rather than actual...
- Extrasolar moon
An extrasolar moon, or exomoon, is a term that refers to a smaller, natural satellite that orbits an extrasolar planet or other extrasolar body more massive than itself.- Definition of satellites around brown dwarfs :...
- Rogue planet
Rogue Planet may refer to:In literature:* Rogue Planet , a Dan Dare story that ran in the original Eagle comic from Volume 6, Issue 48 to Volume 8, Issue 7* Rogue Planet , a novel set in the Star Wars galaxy...
- Sub-brown dwarf
A sub-brown dwarf is a planetary-mass object whose mass is smaller than the low-mass cut-off for brown dwarfs . Unlike proper brown dwarfs, they are not massive enough to fuse deuterium. Sub-brown dwarfs are formed in the manner of stars, through the collapse of a gas cloud, and not through...
- HD 172555
HD 172555 is a white-hot A5V star located relatively close by, 95 light years from Earth in the direction of the constellation Pavo. Spectrographic evidence indicates a relatively recent collision between two planet-sized bodies that destroyed the smaller of the two, which was about the size of...
External links