Mu Arae
Encyclopedia : M : MU : MUA : Mu Arae
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|}Mu Arae (μ Ara / μ Arae) is a 5th magnitude yellow-orange G-type star similar to our Sun. It lies about 49.8 light years away and is found in the constellation Ara (the Altar), where it is visible with the naked eye. It is estimated to have about 108% of the Sun's mass and may be about 32% larger. It has about 1.7 times the luminosity of the Sun and is suspected to be older, moving into the subgiant phase of its stellar evolution. Mu Arae is metal-rich, even more so than our Sun. Based on its chromospheric activity, its age is estimated at approximately 6000 million years.
Planets
As of August 25, 2004, there were three planets believed to be orbiting Mu Arae. Two are suspected to be gas giants, and one may be a terrestrial planet or a low mass gas giant.Mu Arae d
Mu Arae d at the time of its discovery was the least massive extrasolar planet found around a main sequence star. Its discovery was announced on August 25, 2004. Its minimum mass is just 14 times that of Earth. It orbits very close to Mu Arae, completing one revolution every 9.5 days. The discovery was made with the aid of the High Accuracy Radial Velocity Planet Searcher (HARPS) spectrograph, at the European Southern Observatory's La Silla Observatory in Chile. The data that revealed the presence of this planet was gathered on 8 nights of observations in June 2004.
According to current models of planet formation, ESO scientists believe that μ Arae d is likely to be a rocky planet, not a gas giant; 14 Earth masses is theoretically the maximum size for a terrestrial planet. A rocky planet this size could certainly have formed, since Mu Arae has a higher metallicity than our Sun. If this is the case, Mu Arae d may be the first rocky planet discovered outside our Solar System orbiting a main sequence star. The surface of the planet must be very hot because of its closeness to Mu Arae; it is estimated that the surface temperature would be about 900 K. Its surface would likely be volcanic. The probability of life as we know it existing on this planet is thus extremely small. An alternative possibility is that this planet is a small gas giant similar to Uranus or Neptune.
None of the three planets orbiting Mu Arae are directly visible from Earth using currently available tools. All three were found using the radial velocity method of extrasolar planet detection.
Mu Arae b
Mu Arae b is at least one and a half times the mass of Jupiter and orbits within the star's habitable zone. Its orbital period is 650 days. This planet's discovery was announced December 12, 2002.
Mu Arae c
Mu Arae c was announced on June 13, 2002. It is a gas giant at least three times as massive as Jupiter, and has a highly eccentric orbit that makes its distance from the star vary significantly over the course of an orbit.
References
See also
- Extrasolar planet
- List of stars with confirmed extrasolar planets
- PSR 1257+12 - the star with the lightest planets found which are possibly terrestrial.
External links
- * [HD 160691 b]
- * [HD 160691 c]
- * [HD 160691 d]
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