HD 69830
Encyclopedia : H : HD : HD6 : HD 69830
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HD 69830 is an orange dwarf star approximately 41 light-years away in the constellation Puppis. Having a mass, radius, and luminosity smaller than the sun, a planet similar to Earth would have to orbit HD 69830 about 0.75 AU from it. The closest known star to HD 69830 is the red dwarf star L 675-81 about 8.5 light-years from it.
In 2005, an asteroid belt was discovered using the Spitzer Space TelescopeBeichman et al ApJ. 626, 1061, 2005. But HD 69830 made news in 2006 with the announcement of three Neptune-mass extrasolar planets orbiting the starLovis et al. [An extrasolar planetary system with three Neptune‐mass planets], Nature, 18 May 2006.
Planetary system
HD 69830 is the first extrasolar planetary system around a Sun‐like star without any planets comparable to Jupiter or Saturn in mass.
The outermost planet discovered appears to be within the system's habitable zone, where liquid water would remain stable (more accurate data on the primary star's luminosity will be required to know for sure where the habitable zone is). It is believed to be the outer shepherd of the system's asteroid belt. The planets have masses of 10, 12 and 18 times that of Earth, and orbit about the star with periods of about 9, 32 and 197 days, respectively.
The planets were discovered using the HARPS spectrograph on the European Southern Observatory's 3.6-metre La Silla telescope in the Atacama desert, Chile.
| Companion (In order from star) | (Jupiter (planet)>MJ) | Orbital period (days) | (Astronomical unit>AU) | Eccentricity |
|---|---|---|---|---|
| b | >0.033 | 8.667 ± 0.003 | 0.0785 | 0.1 ± 0.04 |
| c | >0.038 | 31.56 ± 0.04 | 0.186 | 0.13 ± 0.06 |
| d | >0.058 | 197 ± 3 | 0.63 | 0.07 ± 0.07 |
Asteroid belt
In 2005, the Spitzer Space Telescope detected dust in the HD 69830 system consistent with the existence of an asteroid belt twenty times more massive than that in our own system lying inside an orbit equivalent to that of Venus in our own solar system. The belt would be so massive 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.
In our own solar system, Jupiter marshals the outer edge of the asteroid belt, preventing the belt from spreading to greater distances. It is likely that HD 69830 d plays a similar role in this system.
References
External links
- [SST: Signs of Alien Asteroid Belt]
- [SolStation: HD 69830 / HR 3259]
- [SPACE.com: Planets Found in Potentially Habitable Setup (May 17,2006)]
- [SpaceDaily: Trio Of Neptunes And Their Belt (May 18,2006)]
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