K2-229
| Observation data EpochJ2000EquinoxJ2000 | |
|---|---|
| Constellation | Virgo |
| Right ascension | 12h27m29.5848s[1] |
| Declination | −06° 43′ 18.7660″[1] |
| Apparent magnitude(V) | 10.985 |
| Characteristics | |
| Evolutionary stage | Main sequence |
| Spectral type | K2V[2] |
| Astrometry | |
| Proper motion(μ) | RA:−80.886±0.131[1]mas/yr Dec.:7.434±0.090[1]mas/yr |
| Parallax(π) | 9.7229 ± 0.1020mas[1] |
| Distance | 335 ± 4ly (103 ± 1pc) |
| Details | |
| Mass | 0.837+0.019 −0.025[2]M☉ |
| Radius | 0.793+0.032 −0.020[2]R☉ |
| Luminosity | ~0.407[3]L☉ |
| Surface gravity(logg) | 4.56+0.03 −0.05[2]cgs |
| Temperature | 5185 ± 32[2]K |
| Metallicity[Fe/H] | −0.06 ± 0.02[2]dex |
| Rotation | 18.1 ± 0.3days[2] |
| Rotational velocity(vsini) | 2.4 ± 0.5[2]km/s |
| Age | 5.4+5.2 −3.7[2]Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
K2-229(also designatedEPIC 228801451orTYC 4947-834-1) is a K-type main sequence star approximately 103parsecs(335 light years) away in the constellationVirgo.It was observed by theKepler Space Telescopeduring its K2 "Second Light" mission in Campaign 10.
Planetary system
[edit]As of March 27, 2018, K2-229 has a system of three confirmedexoplanets.
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | 2.59 (± 0.43)M🜨 | 0.012888 | 0.584249 | 0 (assumed) | 83.9 ± 2.8° | 1.165+0.066 −0.048R🜨 |
| c | <21.3M🜨 | 0.07577 | 8.32834 | 0 (assumed) | 87.94 ± 0.18° | 2.12+0.11 −0.08R🜨 |
| d | <25.1M🜨 | 0.1820 ± 0.00042 | 31.0 ± 1.1 | 0.39 ± 0.29 | 88.92 ± 0.24° | 2.64 ± 0.24R🜨 |
All three known planets transit their star and would orbit inside that ofMercuryif placed in theSolar System.Only the innermost has a well determined mass and composition.
- K2-229b
K2-229b is aSuper-Earthwith aniron-richcomposition. It is about 17% larger thanEarthby radius, but is almost 2.6 times more massive. Its high density indicates it has a core-mass fraction of about 68%, nearly identical to that of Mercury. It is believed that like Mercury, the huge core of K2-229 is the result of a giant impact event. However, unlike Mercury, it orbits extremely close to its host star, with one orbit taking a little over 14 hours to complete. K2-229b has a temperature of over 1,960 K to 2,330 K, hot enough to melt iron and likely giving it an atmosphere of silicate vapor.[2]
- K2-229c
K2-229c is aMini-Neptunesized planet with a radius of 2.12R🜨.Its mass has not been accurately determined, so only an upper limit of 21.3MEcan be given. However, a different method of radial velocity analysis gives the planet's mass at about 9.5ME.With an orbital period of 8.32 days, K2-229c has an equilibrium temperature of 800 K (527 °C; 980 °F) and a dayside temperature of 962 K (689 °C; 1,272 °F).[2]
- K2-229d
K2-229d is another Mini-Neptune with a radius of 2.64R🜨,meaning it is likely gaseous. Only a maximum mass of 25.1MEcould be determined. The planet was detected by a single transit event lasting about two and a half hours long. There were two models for its orbital period: one where it took about 31 days to orbit and the second transit was during a large data gap; and another where it took over 50 days to orbit. The latter scenario was considered unlikely, as K2-229d would need to have a very eccentric orbit to exhibit such a short transit duration – so eccentric that its periapsis would cross the orbit of K2-229c and destabilize the system. It has an equilibrium temperature of 522 K (249 °C; 480 °F).[2]
See also
[edit]References
[edit]- ^abcdeBrown, A. G. A.;et al. (Gaia collaboration) (August 2018)."GaiaData 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 sourceatVizieR.
- ^abcdefghijklmSanterne, A.; Brugger, B.; Armstrong, D. J.; Adibekyan, V.; Lillo-Box, J.; Gosselin, H.; Aguichine, A.; Almenara, J.-M.; Barrado, D.; Barros, S. C. C.; Bayliss, D.; Boisse, I.; Bonomo, A. S.; Bouchy, F.; Brown, D. J. A.; Deleuil, M.; Delgado Mena, E.; Demangeon, O.; Díaz, R. F.; Doyle, A.; Dumusque, X.; Faedi, F.; Faria, J. P.; Figueira, P.; Foxell, E.; Giles, H.; Hébrard, G.; Hojjatpanah, S.; Hobson, M.; et al. (2018). "An Earth-sized exoplanet with a Mercury-like composition".Nature Astronomy.2(5): 393–400.arXiv:1805.08405.Bibcode:2018NatAs...2..393S.doi:10.1038/s41550-018-0420-5.S2CID73667350.
- ^"HEC: Exoplanets Calculator - Planetary Habitability Laboratory @ UPR Arecibo".Archived fromthe originalon 2019-06-02.Retrieved2018-06-17.
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