HD 210702
HD 210702 is an orange subgiant star located approximately 177 light-years away in the constellation of Pegasus. With a mass of 1.8 times that of the Sun, the star spent its main-sequence life as an A-type star. The visual luminosity is 11.38 times that of the Sun and the magnitude is near the naked-eye limit, but binoculars can easily see it.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Pegasus |
| Right ascension | 22h 11m 51.3309s[1] |
| Declination | +16° 02′ 25.9959″[1] |
| Apparent magnitude (V) | 5.939 |
| Characteristics | |
| Spectral type | K1IV |
| U−B color index | 0.73 |
| B−V color index | 0.951[2] |
| R−I color index | 0.49 |
| Astrometry | |
| Radial velocity (Rv) | 10.9 ± 2 km/s |
| Proper motion (μ) | RA: −3.241±0.156[1] mas/yr Dec.: −17.156±0.160[1] mas/yr |
| Parallax (π) | 18.4231 ± 0.0783[1] mas |
| Distance | 177.0 ± 0.8 ly (54.3 ± 0.2 pc) |
| Absolute magnitude (MV) | 2.201 |
| Details | |
| Mass | 1.68 (1.50–1.84)[2] M☉ |
| Radius | 5.2314±0.1171[3] R☉ |
| Luminosity | 12.838±0.5569[3] L☉ |
| Surface gravity (log g) | 3.19 ± 0.08[2] cgs |
| Temperature | 4780±18[3] K |
| Metallicity [Fe/H] | 0.03 [3] dex |
| Age | 5.0[3] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Planetary system
The star shows variability in its radial velocity consistent with a planet-mass companion in a Keplerian orbit,[5] and one was duly discovered in April 2007, from observations at Lick and Keck Observatories in Mount Hamilton (California) and Mauna Kea (Hawai'i), United States.
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥1.808±0.097 MJ | 1.148±0.057 | 354.10±0.70 | 0.028±0.034 | — | — |
References
- Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- Sato, Bun'ei; et al. (2012). "Substellar Companions to Seven Evolved Intermediate-Mass Stars". Publications of the Astronomical Society of Japan. 64 (6). 135. arXiv:1207.3141. Bibcode:2012PASJ...64..135S. doi:10.1093/pasj/64.6.135.
- von Braun, Kaspar; et al. (2014). "Stellar diameters and temperatures – V. 11 newly characterized exoplanet host stars". Monthly Notices of the Royal Astronomical Society. 438 (3): 2413–2425. arXiv:1312.1792. Bibcode:2014MNRAS.438.2413V. doi:10.1093/mnras/stt2360.
- "HD 210702". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-09-15.
- Johnson, John Asher; et al. (2007). "Retired A Stars and Their Companions: Exoplanets Orbiting Three Intermediate-Mass Subgiants". The Astrophysical Journal. 665 (1): 785–793. arXiv:0704.2455. Bibcode:2007ApJ...665..785J. doi:10.1086/519677.
- Luhn, Jacob K.; et al. (2019). "Retired A Stars and Their Companions. VIII. 15 New Planetary Signals around Subgiants and Transit Parameters for California Planet Search Planets with Subgiant Hosts". The Astronomical Journal. 157 (4). 149. arXiv:1811.03043. Bibcode:2019AJ....157..149L. doi:10.3847/1538-3881/aaf5d0.
- "HR 8461". webviz.u-strasbg.fr/.
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