Gliese 581e // or Gl 581e is an extrasolar planet orbiting within the Gliese 581 system, located approximately 20.4 light-years away from Earth in the Libra constellation. It is the third planet discovered in the system (fourth if the disputed planet candidate Gliese 581d is included) and the first in order from the star.
Size comparison of Gliese 581e with Earth.
(Based on selected hypothetical modeled compositions)
|Discovered by||Mayor et al.|
|Discovery site||La Silla Observatory, Chile|
|Discovery date||21 April 2009|
|0.02815 ± 0.00006 AU (4,211,200 ± 9,000 km)|
|Eccentricity||0.00 ± 0.06|
|3.1490 ± 0.0002 d|
|2454752.33 ± 0.05|
|Semi-amplitude||1.7 ± 0.2|
The planet was discovered by an Observatory of Geneva team led by Michel Mayor, using the HARPS instrument on the European Southern Observatory 3.6 m (140 in) telescope in La Silla, Chile. The discovery was announced on 21 April 2009. Mayor's team employed the radial velocity technique, in which the orbit size and mass of a planet are determined based on the small perturbations it induces in its parent star's orbit via gravity.
At a minimum mass of 1.7 Earth masses, it is one of the least massive extrasolar planets discovered around a normal star, and relatively close in mass to Earth. It is also the exoplanet with the smallest accurate true mass known. At an orbital distance of just 0.03 AU (4,500,000 km) from its parent star, however, it orbits further in than the habitable zone. It is unlikely to possess an atmosphere due to its high temperature and strong radiation from the star. Although scientists think it probably has a rocky surface similar to Earth, it is also likely to experience intense tidal heating similar to (and likely more intense than) that affecting Jupiter's moon Io. Gliese 581e completes an orbit around its parent star in approximately 3.15 days.
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- Mayor, M.; Bonfils, X.; Forveille, T.; et al. (2009). "The HARPS search for southern extra-solar planets, XVIII. An Earth-mass planet in the GJ 581 planetary system". Astronomy and Astrophysics. 507 (1): 487–494. arXiv:0906.2780. Bibcode:2009A&A...507..487M. doi:10.1051/0004-6361/200912172.
- Barnes, Rory; Jackson, Brian; Greenberg, Richard; Raymond, Sean N. (2009-06-09). "Tidal Limits to Planetary Habitability". The Astrophysical Journal. 700: L30–L33. arXiv:0906.1785. Bibcode:2009ApJ...700L..30B. doi:10.1088/0004-637X/700/1/L30.
- Rincon, Paul; Amos, Jonathan (2009-04-21). "Lightest exoplanet is discovered". BBC. Retrieved 2009-04-21.
- Overbye, Dennis (April 21, 2009). "Astronomers Find Planet Closer to Size of Earth". New York Times.