Astronomy:HD 210702
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Pegasus[1] |
| Right ascension | 22h 11m 51.331s[2] |
| Declination | +16° 02′ 26.00″[2] |
| Apparent magnitude (V) | 5.93[1] |
| Characteristics | |
| Evolutionary stage | subgiant[3] |
| Spectral type | K1 III[4] or K1 IV[3] |
| B−V color index | 0.951±0.001[1] |
| Astrometry | |
| Radial velocity (Rv) | 18.4593±0.0392[5] km/s |
| Proper motion (μ) | RA: −3.263±0.156[2] mas/yr Dec.: −17.296±0.036[2] mas/yr |
| Parallax (π) | 18.4593 ± 0.0392[2] mas |
| Distance | 176.7 ± 0.4 ly (54.2 ± 0.1 pc) |
| Absolute magnitude (MV) | 2.14[3] |
| Details | |
| Mass | 1.47±0.04[6] M☉ |
| Radius | 4.9±0.1[6] R☉ |
| Luminosity | 12.9±0.1[6] L☉ |
| Surface gravity (log g) | 3.2200±0.074[7] cgs |
| Temperature | 4,946±32[6] K |
| Metallicity [Fe/H] | 0.083±0.027[7] dex |
| Rotational velocity (v sin i) | 2.50±0.48[7] km/s |
| Age | 3.1±0.3[6] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
HD 210702 is a star with an orbiting exoplanet in the northern constellation of Pegasus.[1] It has an apparent visual magnitude of 5.93,[1] which is bright enough that the star is dimly visible to the naked eye. The distance to HD 210702 is 177 light years based on parallax measurements, and it is drifting further away with a radial velocity of 18.5 km/s.[5] It is a probable member of the Ursa Major moving group, an association of co-moving stars.[4]
Although a stellar classification of K1 III[4] suggests this is an evolved giant star, it is more likely to be a subgiant star currently at the based of the red giant branch.[9] Currently 3[6] billion years old, HD 210702 spent its main-sequence life as an A-type star. Consistent with its evolutionary status, it has little or no magnetic activity in its chromosphere.[10] The star has 1.5[6] times the mass of the Sun and has expanded to 4.9 times the Sun's radius. It is radiating 12.9 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,946 K.[6]
Planetary system
The star shows variability in its radial velocity consistent with an exoplanetary companion in a Keplerian orbit,[10] 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. As the inclination of the orbital plane is unknown, only a lower bound on the mass of this object can be estimated. It has at least 1.8 times the mass of Jupiter.[9]
| 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 | — | — |
See also
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A.
- ↑ 2.0 2.1 2.2 2.3 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 3.0 3.1 3.2 Sato, Bun'ei et al. (2012). "Substellar Companions to Seven Evolved Intermediate-Mass Stars". Publications of the Astronomical Society of Japan 64 (6): 135. doi:10.1093/pasj/64.6.135. Bibcode: 2012PASJ...64..135S.
- ↑ 4.0 4.1 4.2 Levato, H.; Abt, H. A. (August 1978). "Spectral types in the Ursa Major stream". Publications of the Astronomical Society of the Pacific 90: 429−433. doi:10.1086/130352. Bibcode: 1978PASP...90..429L.
- ↑ 5.0 5.1 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G. Gaia DR2 record for this source at VizieR.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 Bonfanti, A. et al. (2016). "Age consistency between exoplanet hosts and field stars". Astronomy & Astrophysics 585: 14. doi:10.1051/0004-6361/201527297. A5. Bibcode: 2016A&A...585A...5B.
- ↑ 7.0 7.1 7.2 Hojjatpanah, S. et al. (2019). "Catalog for the ESPRESSO blind radial velocity exoplanet survey". Astronomy and Astrophysics 629: A80. doi:10.1051/0004-6361/201834729. Bibcode: 2019A&A...629A..80H.
- ↑ "HD 210702". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+210702.
- ↑ 9.0 9.1 9.2 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. doi:10.3847/1538-3881/aaf5d0. Bibcode: 2019AJ....157..149L.
- ↑ 10.0 10.1 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. doi:10.1086/519677. Bibcode: 2007ApJ...665..785J.
Further reading
- 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. doi:10.1093/mnras/stt2360. Bibcode: 2014MNRAS.438.2413V.
- "HR 8461". webviz.u-strasbg.fr/. http://webviz.u-strasbg.fr/viz-bin/VizieR-S?HR%208461.
Coordinates: 
22h 11m 51.3311s, +16° 02′ 25.983″
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