The innermost planet is most probably rocky, while the outermost is the first known Neptune-mass planet to reside in its host star's habitable zone; the outermost planet is also thought to serve as the shepherd for HD 69830's asteroid belt in the same way that Jupiter marshals the outer edge of the asteroid belt of the solar system, preventing the belt from spreading to greater distances.
The trio of Neptune-mass planets around HD 69830 were found by a team of European astronomers using the HARPS spectrograph on ESO's 3.6-meter telescope at La Silla, Chile. The discovery was announced in 2006.1
Dust diskIn 2005, the Spitzer Space Telescope detected dust in the HD 69830 system consistent with the existence of an asteroid belt 20 times more massive than that in our own system lying inside an orbit similar to that of Venus.2 The belt would be so luminous that the nights on any nearby planets would be lit up by zodiacal light 1000 times brighter than that seen on Earth, easily outshining the Milky Way.
Alternatively, the detected dust could be caused by the evaporation of a Pluto-sized comet gravitationally perturbed into a close orbit around its star. Indeed, the dust chemistry, which includes a form of olivine called forsterite, is strikingly similar to that of Comet Hale-Bopp. However, the odds that Spitzer happened to detect a supercomet spiraling in towards its star, a rare event of short duration, are slim.
Related categories NOTABLE STARS
EXTRASOLAR PLANETS AND SUBSTELLAR OBJECTS
Sources: ESO and Wikipedia
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