Epoch 2000 Equinox 2000
|Right ascension||19h 05m 20.7735s|
|Declination||+25° 55′ 14.379″|
|Apparent magnitude (V)||7.175|
|Absolute magnitude (V)||3.319|
|Spectral type||K0 IV|
HD 177830 is a 7th magnitude star located approximately 190 light-years away in the constellation of Lyra. It is slightly more massive than our Sun, but cooler being a type K star. Therefore it is a subgiant clearly more evolved than the Sun. In visual light it is four times brighter than the Sun, but because of its distance, about 190 light years, it is not visible to the unaided eye. With binoculars it should be easily visible.
The star is known to have two extrasolar planets orbiting around it.
On November 14, 1999, the discovery of a planet HD 177830 b was announced by the California and Carnegie Planet Search team using the very successful radial velocity method along with two other planets. This planet is nearly 50% more massive than Jupiter and takes 407 days to orbit the star in an extremely circular orbit. In 2000 a group of scientists proposed, based on preliminary Hipparcos astrometrical satellite data, that the orbital inclination of HD 177830 b is as little as 1.3°. If that was the case, the planet would have a mass of 67 times that of Jupiter making it a brown dwarf instead of a planet. However, it is very unlikely that the planet would have such orbit. Furthermore, brown dwarfs with short orbits around solar-mass stars are exceedingly rare (the so-called "brown dwarf desert") making the claim even more unlikely.
On November 17, 2010, the discovery of a second planet HD 177830 c was announced along with four other planets. The planet has 50% the mass of Saturn and takes 111 days to orbit the star in a very eccentric orbit. This planet is in a near 4:1 resonance with the outer planet.
(in order from star)
|c||≥0.15 ± 0.03 MJ||0.5137 ± 0.0006||110.9 ± 0.3||0.3495 ± 0.0002||—||—|
|b||≥1.49 ± 0.03 MJ||1.2218 ± 0.0008||406.6 ± 0.4||0.009 ± 0.004||—||—|
- Vogt et al.; Marcy, Geoffrey W.; Butler, R. Paul; Apps, Kevin (2000). "Six New Planets from the Keck Precision Velocity Survey". The Astrophysical Journal 536 (2): 902–914. arXiv:astro-ph/9911506. Bibcode:2000ApJ...536..902V. doi:10.1086/308981.
- Meschiari et al. (2011). "The Lick-Carnegie Survey: Four New Exoplanet Candidates". arXiv:1011.4068 [astro-ph.EP].
- "HD 177830". Extrasolar Visions. Retrieved 2008-08-30.
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