Gliese 581b
| Exoplanet | List of exoplanets | |
|---|---|---|
 (Based on selected hypothetical modeled compositions) |
||
| Parent star | ||
| Star | Gliese 581 | |
| Constellation | Libra | |
| Right ascension | (α) | 15h 19m 26s |
| Declination | (δ) | −07° 43′ 20″ |
| Apparent magnitude | (mV) | 10.56 to 10.58 |
| Distance | 20.37 ± 0.3 ly (6.26 ± 0.1 pc) |
|
| Spectral type | M3V | |
| Mass | (m) | 0.31 M☉ |
| Radius | (r) | 0.29 R☉ |
| Temperature | (T) | 3480 ± 48 K |
| Metallicity | [Fe/H] | -0.33 ± 0.12 |
| Age | 7 – 11 Gyr | |
| Orbital elements | ||
| Semi-major axis | (a) | 0.04061 ± 0.0001AU |
| Eccentricity | (e) | 0.00 ± 0.03 |
| Orbital period | (P) | 5.3686 ± 0.0001d |
| Time of periastron | (T0) | 2454751.76 ± 0.01JD |
| Semi-amplitude | (K) | 12.6 ± 0.2m/s |
| Physical characteristics | ||
| Minimum mass | (m sin i) | 15.8 ± 0.3M⊕ |
| Stellar flux | (F⊙) | 7.9 ⊕ |
| Discovery information | ||
| Discovery date | August 22, 2005 announced November 30, 2005 |
|
| Discoverer(s) | X. Bonfils, T. Forveille, X. Delfosse, S. Udry, M. Mayor, C. Perrier, F. Bouchy, F. Pepe, D. Queloz, J.-L. Bertaux |
|
| Discovery method | Doppler Spectroscopy | |
| Discovery status | Published | |
| Other designations | ||
|
HO Librae b, HO Lib b, BD−07°4003 b, GJ 581 b, HIP 74995 b, LFT 1195 b, LHS 394 b, LPM 564 b, LTT 6112 b, NLTT 39886 b, TYC 5594-1093-1 b, Wolf 562 b
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| Database references | ||
| Extrasolar Planets Encyclopaedia |
data | |
| SIMBAD | data | |
| Exoplanet Archive | data | |
| Open Exoplanet Catalogue | data | |
Gliese 581b or Gl 581b is an extrasolar planet orbiting within the Gliese 581 planetary system. It is the first planet of three discovered in the system so far, and the second in order from the star.
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.
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 AU). By comparison, Mercury is 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 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. Since Gliese 581b does not transit, nothing more can be said of it yet. At the least, given that Gliese 581b orbits alongside two other planets (Gliese 581c and e) and that Gliese 436 b (thus far) stands alone, their formation must have differed.
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