Gliese 581b

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Gliese 581 b
Exoplanet List of exoplanets
Exoplanet Comparison Gliese 581 b.png
Size comparison of Gliese 581 b with Neptune.
(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 ± 0.0001[1] AU
Eccentricity (e) 0.00 ± 0.03[1]
Orbital period (P) 5.3686 ± 0.0001[1] d
Time of periastron (T0) 2454751.76 ± 0.01[1] JD
Semi-amplitude (K) 12.6 ± 0.2[1] m/s
Physical characteristics
Minimum mass (m sin i) 15.8 ± 0.3[1] M
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
Database references
Extrasolar Planets
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.[2][3]


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.[4]

Orbit and mass[edit]

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.[5] 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.

See also[edit]


  1. ^ a b c d e f Robertson, Paul; Mahadevan, Suvrath; Endl, Michael; Roy, Arpita (3 July 2014). "Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581". Science. 345: 440–444. Bibcode:2014Sci...345..440R. arXiv:1407.1049Freely accessible. doi:10.1126/science.1253253. 
  2. ^ Gl 581 b
  3. ^ If There's Life on Alien Planet Gliese 581g, How Do We Find It?
  4. ^ X. Bonfils; et al. (2005). "The HARPS search for southern extra-solar planets VI: A Neptune-mass planet around the nearby M dwarf Gl 581". Astronomy and Astrophysics Letters. 443 (3): L15–L18. Bibcode:2005A&A...443L..15B. arXiv:astro-ph/0509211Freely accessible. doi:10.1051/0004-6361:200500193. 
  5. ^ M. Lopez-Morales; et al. (2006). "Limits to Transits of the Neptune-mass planet orbiting Gl 581". Publications of the Astronomical Society of the Pacific. 118 (849): 1506–1509. Bibcode:2006PASP..118.1506L. arXiv:astro-ph/0609255Freely accessible. doi:10.1086/508904. 

External links[edit]

Coordinates: Sky map 15h 19m 26s, −07° 43′ 20″