Gliese 581b is an extrasolar planet, orbiting the star Gliese 581. It is the second planet in order from the star of the three discovered in the system so far. The planet was discovered by a team of French and Swiss astronomers, who announced their findings on November 30, 2005.
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 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 star (after Gliese 876's planets and Gliese 436 b).
The planet was discovered using the HARPS 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 massEdit
Gliese 581b has a minimum mass of approximately 15.8 times the Earth's mass, which makes it similar to Neptune's mass. This implies that the planet may be a Hot Neptune. 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 an orbit in only 5.4 days, at a mean distance of about 6 million kilometers (0.041 AU). In comparison, Mercury, the closest planet to the Sun, orbits at a distance of 58 million kilometers (0.387 AU), and completes an orbit in 88 days.
Gliese 581b is about 0.04 AU from Gliese 581. It is likely close to Gliese 436 b in mass, temperature, and susceptibility to solar effects such as coronal mass ejection. Since Gliese 581b does not transit its star, not much is known about its characteristics. At least given that Gliese 581b orbits alongside two other planets (Gliese 581 c and e) and that Gliese 436 b (thus far) stands alone, their formation must have differed.