Gliese 581b or Gl 581b is an extrasolar planet orbiting within the Gliese 581 system. 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 astronomers, 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's planets and Gliese 436 b). 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''.

Orbit and mass

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

day A day is the time period of a full rotation of the Earth with respect to the Sun. On average, this is 24 hours, 1440 minutes, or 86,400 seconds. In everyday life, the word "day" often refers to a solar day, which is the length between two so ...

s 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 Gliese 436 b 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. 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