HD 179070
HD 179070 also known as Kepler-21 is a F-type subgiant star. A transiting exoplanet was discovered orbiting this star by the Kepler spacecraft.[4] At a magnitude of 8.25 this was the brightest star observed by Kepler to host a validated planet until the discovery of an exoplanet orbiting HD 212657 in 2018.[3][8]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Lyra[1] |
| Right ascension | 19h 09m 26.8351s[2] |
| Declination | +38° 42′ 50.455″[2] |
| Apparent magnitude (V) | 8.25[3] |
| Characteristics | |
| Spectral type | F6IV[4] |
| Apparent magnitude (J) | 7.229±0.032[5] |
| Apparent magnitude (H) | 7.031±0.023[5] |
| Apparent magnitude (K) | 6.945±0.018[5] |
| Variable type | Planetary transit variable[4] |
| Astrometry | |
| Proper motion (μ) | RA: 27.951±0.054[2] mas/yr Dec.: 28.585±0.056[2] mas/yr |
| Parallax (π) | 9.1859 ± 0.0323[2] mas |
| Distance | 355 ± 1 ly (108.9 ± 0.4 pc) |
| Details[6] | |
| Mass | 1.408+0.021 −0.030 M☉ |
| Radius | 1.902+0.018 −0.012 R☉ |
| Luminosity | 5.188+0.142 −0.128 L☉ |
| Surface gravity (log g) | 4.026±0.004 cgs |
| Temperature | 6305±50 K |
| Metallicity [Fe/H] | −0.03±0.10 dex |
| Rotation | 12.62±0.03 d[3] |
| Rotational velocity (v sin i) | 8.4±0.5[3] km/s |
| Age | 2.60±0.16 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
Planetary system
The single known planet orbiting this star was identified as a candidate based on photometry from the first four months of data from the Kepler spacecraft.[9] Confirmation was obtained in 2012 after extensive follow-up observations and analysis of the Kepler light curves.[4]
The calculated density of the planet is approximately 6.4 g cm−3, similar to earth's 5.5 g cm−3, which suggests a rocky composition. With an equilibrium temperature of 2025 Kelvin, the top few-hundred kilometers of the planet is probably molten.[3]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| Kepler-21b | 5.08±1.72 M⊕ | 0.0427172±0.0000003 | 2.7858212±0.0000032 | 0.02±0.1 | 83.20+0.28 −0.26° |
1.639+0.019 −0.015 R⊕ |
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References
- Roman, Nancy G. (1987). "Identification of a Constellation From a Position". Publications of the Astronomical Society of the Pacific. 99 (617): 695–699. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Vizier query form
- 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.
- López-Morales, Mercedes; et al. (2016). "Kepler-21b: A Rocky Planet Around a V = 8.25 Magnitude Star". The Astronomical Journal. 152 (6). 204. arXiv:1609.07617. Bibcode:2016AJ....152..204L. doi:10.3847/0004-6256/152/6/204.
- Howell, Steve B.; et al. (2012). "Kepler-21b: A 1.6 REarth Planet Transiting the Bright Oscillating F Subgiant Star HD 179070". The Astrophysical Journal. 746 (2). 123. arXiv:1112.2165. Bibcode:2012ApJ...746..123H. doi:10.1088/0004-637X/746/2/123.
- Skrutskie, M. F.; et al. (2006). "The Two Micron All Sky Survey (2MASS)". The Astronomical Journal. 131 (2): 1163–1183. Bibcode:2006AJ....131.1163S. doi:10.1086/498708.Vizier catalog entry
- Silva Aguirre, V.; et al. (2015). "Ages and fundamental properties of Kepler exoplanet host stars from asteroseismology". Monthly Notices of the Royal Astronomical Society. 452 (2): 2127–2148. arXiv:1504.07992. Bibcode:2015MNRAS.452.2127S. doi:10.1093/mnras/stv1388.
- "HD 179070". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-06-10.
- Mayo, Andrew W.; et al. (2018). "275 Candidates and 149 Validated Planets Orbiting Bright Stars in K2 Campaigns 0–10". The Astronomical Journal. 155 (3). 136. arXiv:1802.05277. Bibcode:2018AJ....155..136M. doi:10.3847/1538-3881/aaadff.
- Borucki, William J.; et al. (2011). "Characteristics of Planetary Candidates Observed by Kepler. II. Analysis of the First Four Months of Data". The Astrophysical Journal. 736 (1). 19. arXiv:1102.0541. Bibcode:2011ApJ...736...19B. doi:10.1088/0004-637X/736/1/19.
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