Mu Arae d
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- This article is about the 9-day Uranus-mass planet in the Mu Arae system. For the 310-day planet, which some authors refer to as Mu Arae d, see Mu Arae e.
| Extrasolar planet | Lists of extrasolar planets | |
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| Parent star | ||
| Star | Mu Arae | |
| Constellation | Ara | |
| Right ascension | (α) | 17h 44m 08.7s |
| Declination | (δ) | −51° 50′ 03″ |
| Spectral type | G3IV–V | |
| Orbital elements | ||
| Semimajor axis | (a) | 0.09094 AU |
| Eccentricity | (e) | 0.172 ± 0.04 |
| Orbital period | (P) | 9.6386 ± 0.0015 d |
| Inclination | (i) | ?° |
| Longitude of periastron |
(ω) | ?° |
| Time of periastron | (τ) | 2452991 ± 0.4 JD |
| Physical characteristics | ||
| Mass | (m) | >0.03321 MJ (>10.5 ME) |
| Radius | (r) | ? RJ |
| Density | (ρ) | ? kg/m3 |
| Temperature | (T) | ~900 K |
| Discovery information | ||
| Discovery date | 2004 | |
| Discoverer(s) | Santos, Bouchy Mayor, Pepe |
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| Detection method | Doppler Spectroscopy | |
| Discovery status | Published | |
| Other designations | ||
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Mu Arae c
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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 four planets orbiting Mu Arae are directly visible from Earth using currently available tools. All four were found using the radial velocity method of extrasolar planet detection.
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| Star | Mu Arae |
| Planets | b · c · d · e |
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