HD 177830

HD 177830
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Lyra
Right ascension 19h 05m 20.773s[1]
Declination +25° 55′ 14.38″[1]
Apparent magnitude (V) 7.175
Characteristics
Spectral type K0IV[2]/M4V[3]
Astrometry
Proper motion (μ) RA: −40.84 ± 0.38[1] mas/yr
Dec.: −51.75 ± 0.57[1] mas/yr
Parallax (π)16.94 ± 0.63[1] mas
Distance193 ± 7 ly
(59 ± 2 pc)
Other designations
BD+25°3719, Gliese 743.2, HIP 93746, GSC 02126-01196, SAO 86791.[4]

HD 177830 is a 7th magnitude binary star system located approximately 193 light-years away in the constellation of Lyra. The primary star 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 193 light years, it is not visible to the unaided eye. With binoculars it should be easily visible. The secondary star is a Red dwarf star orbiting at a distance of 100 to 200 AU with a likely period of roughly 800 years.[3]

The primary star is known to have two extrasolar planets orbiting around it.

Planetary system

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 (MJ) and takes 407 days to orbit the star in an extremely circular orbit.[2] 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 MJ, 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 (M☉) 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.[5]

The HD 177830 planetary system[5]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
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 — —

See also

References

  1. 1 2 3 4 5 van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752Freely accessible. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.Vizier catalog entry
  2. 1 2 Vogt, Steven S.; et al. (2000). "Six New Planets from the Keck Precision Velocity Survey". The Astrophysical Journal. 536 (2): 902–914. arXiv:astro-ph/9911506Freely accessible. Bibcode:2000ApJ...536..902V. doi:10.1086/308981.
  3. 1 2 Roberts Jr., Lewis C.; et al. (2015). "Know the Star, Know the Planet. V. Characterization of the Stellar Companion to the Exoplanet Host Star HD 177830". The Astronomical Journal. 150 (4). 103. arXiv:1507.07913Freely accessible. Bibcode:2015AJ....150..103R. doi:10.1088/0004-6256/150/4/103.
  4. ↑ "HD 177830 -- Double or multiple star". SIMBAD Astronomical Database. Centre de données astronomiques de Strasbourg. Retrieved 2014-10-11.
  5. 1 2 Meschiari, Stefano; et al. (2011). "The Lick-Carnegie Survey: Four New Exoplanet Candidates". The Astrophysical Journal. 727 (2). 117. arXiv:1011.4068Freely accessible. Bibcode:2011ApJ...727..117M. doi:10.1088/0004-637X/727/2/117.

Coordinates: 19h 05m 20.7735s, +25° 55′ 14.379″


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