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's mass, similar to Neptune'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 and completes a full orbit in only 5.4 days at a mean distance of about 6 million kilometers (0.041 astronomical unit, AU). By comparison, Mercury (planet), Mercury 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 astronomical unit, AU from its sun. It is likely close to Gliese 436 b in mass, temperature, and (with Gliese 876 d) susceptibility to solar effects such as coronal mass ejection. Gliese 581b does not transit. At the least, given that Gliese 581b orbits alongside two other planets (Gliese 581c and Gliese 581e, e) and that Gliese 436 b (thus far) stands alone, their formation must have differed.
See also
*Habitability of red dwarf systems
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)