HD 69830
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| Observation data Equinox J2000.0 |
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|---|---|
| Constellation | Puppis |
| Right ascension | 08h 18m 23.9473s |
| Declination | -12° 37' 55.824" |
| Apparent magnitude (V) | +5.95 |
| Characteristics | |
| Spectral type | K0V |
| U-B color index | ? |
| B-V color index | 0.753 |
| Variable type | none |
| Astrometry | |
| Radial velocity (Rv) | +30.4 km/s |
| Parallax (π) | 79.48 ± .73 .57 .129 mas |
| Distance | 41 ly (12.6 pc) |
| Absolute magnitude (MV) | ? |
| Details | |
| Mass | 0.86 ± 0.03 M☉ |
| Radius | 0.89 R☉ |
| Luminosity | 0.60 ± 0.03 L☉ |
| Temperature | 5385 ± 20 K |
| Metallicity | 89 ± 4 % |
| Rotation | 21.5 days |
| Age | (7 ± 3) × 109 years |
| Other designations | |
|
HR 3259, Gl 302, HIP 40693, SAO 154093, LHS 245, BD −12°2449
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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 Telescope[1]. But HD 69830 made news in 2006 with the announcement of three Neptune-mass extrasolar planets orbiting the star[2].
Contents |
[edit] 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). 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) |
Mass (MJ) |
Orbital period (days) |
Semimajor axis (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 |
[edit] 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. The belt was originally thought to be located inside an orbit equivalent to that of Venus in our own solar system, which would place it between the orbits of the second and third planets. 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.
Further analysis of the spectrum of the belt revealed that it resembles a disrupted P-type or D-type asteroid, containing many small icy grains which would not survive at close distances to the star. Instead, it seems more likely that the belt is located outside the orbit of the outermost planet, in the 2:1 or 5:2 mean motion resonance.[3]
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.
[edit] References
- ^ Beichman, C.A. et al. (2005). "An Excess Due to Small Grains around the Nearby K0 V Star HD 69830: Asteroid or Cometary Debris?". The Astrophysical Journal 626 (2): 1061 – 1069.
- ^ Lovis, C. et al. (2006). "An extrasolar planetary system with three Neptune-mass planets". Nature 441 (7091): 305 – 309.
- ^ Lisse, C.M. et al. (2007). "On the Nature of the Dust in the Debris Disk Around HD 69830". The Astrophysical Journal 658 (1): 584 – 592.
