Gliese 581b or Gl 581b is an

extrasolar planet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

orbiting within the

Gliese 581 system Gliese 581 () is a red dwarf star of spectral type M3V at the center of the Gliese 581 planetary system, about 20 light years away from Earth in the Libra constellation. Its estimated mass is about a third of that of the Sun, and it is t ...

. It is the first planet discovered of three confirmed in the system so far, and the second in order from the star.

Discovery

The planet was discovered by a team of French and Swiss

astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, natural satellite, moons, comets and galaxy, g ...

s, who announced their findings on November 30, 2005, as a discovery of one of the smallest

extrasolar planets An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

ever found, with one conclusion being that planets may be more common around the smallest stars. It was the fifth planet found around a

red dwarf ''Red Dwarf'' is a British science fiction comedy franchise created by Rob Grant and Doug Naylor, which primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave since 2009, gaining a cult following. T ...

star (after

Gliese 876 Gliese 876 is a red dwarf approximately 15 light-years away from Earth in the constellation of Aquarius. It is one of the closest known stars to the Sun confirmed to possess a planetary system with more than two planets, after Gliese ...

's planets and

Gliese 436 b Gliese 436 b (sometimes called GJ 436 b) is a Neptune-sized exoplanet orbiting the red dwarf Gliese 436. It was the first hot Neptune discovered with certainty (in 2007) and was among the smallest-known transiting planets in mass and radius, un ...

). The planet was discovered using the

HARPS The High Accuracy Radial Velocity Planet Searcher (HARPS) is a high-precision echelle planet-finding spectrograph installed in 2002 on the ESO's 3.6m telescope at La Silla Observatory in Chile. The first light was achieved in February 2003. H ...

instrument, with which they found the host star to have a wobble that implied the existence of the planet. The astronomers published their results in ''

Astronomy and Astrophysics Letters Astronomy () is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, ...

''.

Orbit and mass

Gliese 581b is at a minimum, approximately 15.8 times the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

's mass, similar to

Neptune Neptune is the eighth planet from the Sun and the farthest known planet in the Solar System. It is the fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times ...

's mass. It does not transit its star, implying that its inclination is less than 88.1 degrees. It is rather close to

Gliese 581 Gliese 581 () is a red dwarf star of spectral type M3V at the center of the Gliese 581 planetary system, about 20 light years away from Earth in the Libra constellation. Its estimated mass is about a third of that of the Sun, and it is t ...

and completes a full orbit in only 5.4 days at a mean distance of about 6 million kilometers (0.041 AU). By comparison,

Mercury Mercury commonly refers to: * Mercury (planet), the nearest planet to the Sun * Mercury (element), a metallic chemical element with the symbol Hg * Mercury (mythology), a Roman god Mercury or The Mercury may also refer to: Companies * Merc ...

is at a distance of 58 million kilometers (0.387 AU) and completes an orbit in 88 days.

Characteristics

Gliese 581b is about 0.04 AU from its sun. It is likely close to

in mass, temperature, and (with

Gliese 876 d Gliese 876 d is an exoplanet approximately 15 light-years away in the constellation of Aquarius. The planet was the third planet discovered orbiting the red dwarf Gliese 876. It was the lowest-mass extrasolar planet apart from the pulsar planets o ...

) susceptibility to solar effects such as

coronal mass ejection A coronal mass ejection (CME) is a significant release of plasma and accompanying magnetic field from the Sun's corona into the heliosphere. CMEs are often associated with solar flares and other forms of solar activity, but a broadly accepted ...

. Gliese 581b does not transit. At the least, given that Gliese 581b orbits alongside two other planets (

Gliese 581c Gliese 581c (Gl 581c or GJ 581c) is a planet orbiting within the Gliese 581 system. It is the second planet discovered in the system and the third in order from the star. With a mass at least 5.5 times that of the Earth, it is classified as a s ...

and e) and that Gliese 436 b (thus far) stands alone, their formation must have differed.

References

External links

ESO: The Dwarf that Carries a World

{{DEFAULTSORT:Gliese 581B Exoplanets in the Gliese Catalog Gliese 581 Exoplanets discovered in 2005 Hot Neptunes Libra (constellation)

Discovery

Orbit and mass

Characteristics

See also

References

External links