K2-19

K2-19
Observation data
Epoch J2000      Equinox ICRS
Constellation Virgo[1]
Right ascension 11h 39m 50.4803s[2]
Declination +00° 36′ 12.875″[2]
Apparent magnitude (V) 13.002±0.009[3]
Characteristics
Evolutionary stage main sequence[2]
Spectral type K0 V[4] or G9V[5]
Apparent magnitude (J) 11.596±0.024[6]
Apparent magnitude (H) 11.208±0.022[6]
Apparent magnitude (K) 11.161±0.026[6]
Apparent magnitude (B) 13.798±0.020[3]
Variable type Planetary transit variable[7]
Astrometry
Radial velocity (Rv)−7.2296±0.0080[8] km/s
Proper motion (μ) RA: −18.673(22)‍[2] mas/yr
Dec.: 4.571(15)‍[2] mas/yr
Parallax (π)3.3410±0.0196 mas[2]
Distance976 ± 6 ly
(299 ± 2 pc)
Details[9]
Mass0.892(34) M☉
Radius0.824(24) R☉
Surface gravity (log g)4.556(24) cgs
Temperature5350(110) K
Metallicity [Fe/H]0.03(2) dex
Rotation18.36(51) d
Rotational velocity (v sin i)3.00(50)[4] km/s
Age1.70(25) Gyr
Other designations
UCAC4 454-050261, EPIC 201505350, 2MASS J11395048+0036129, Gaia DR3 3798833775141351552[10]
Database references
SIMBADdata
Exoplanet Archivedata

K2-19 is an early K-type[4] or late G-type main sequence star[5] that is magnetically active, and has a light curve that exhibits variations in brightness of ~1%.[5] It is located approximately 976 light-years away in the constellation Virgo. Three confirmed transiting exoplanets are known to orbit this star.

Planetary system

Discovery

The two outer planets were reported as planet candidates during analysis of data from Campaign 1 of the Kepler space telescope's K2 extended mission.[11] Both planets were confirmed by David J. Armstrong and collaborators, who used ground-based telescopes to detect additional transits and measure hour-long transit-timing variations for K2-19b.[7] They were independently validated along with 20 other planets by Benjamin T. Montet and team.[12]

K2-19d was first reported as a planet candidate during a search for candidates from the first year of the K2 Mission[13] and was later validated by Sinukoff et al.[5]

A fourth possible planet orbiting further out was reported in 2025.[9]

Characteristics

K2-19 has a planetary system with three known planets, of which the two larger ones, K2-19b and K2-19c, are either close to the 3:2 mean motion resonance or inside it.[14][15] All three planets orbit closer to their star than the planet Mercury does to the Sun.[4][16]

The K2-19 planetary system[9]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination
(°)		 Radius
d <6.2 M🜨 0.03478(43) 2.50827+0.00027
−0.00014		 <0.44 89.7(1.6) 1.044(64) R🜨
b 30.8(1.3) M🜨 0.07487(90) 7.922806(90) 0.040(24) 89.70(26) 6.59(22) R🜨
c 11.12(44) M🜨 0.0982(12) 11.89770(46) 0.067(17) 89.37(15) 3.88(14) R🜨
e (candidate) <2.0 M🜨 0.1387(17) 19.9724(54) <0.15 89.20+0.17
−0.43		 1.22(15) R🜨

References

  1. ↑ Roman, Nancy G. (1987). "Identification of a constellation from a position". Publications of the Astronomical Society of the Pacific. 99 (617): 695. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Constellation record for this object at VizieR.
  2. 1 2 3 4 5 6 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. 1 2 Henden, A. A.; et al. (2016). "VizieR Online Data Catalog: AAVSO Photometric All Sky Survey (APASS) DR9 (Henden+, 2016)". VizieR On-line Data Catalog: II/336. Originally Published in: 2015AAS...22533616H. 2336. Bibcode:2016yCat.2336....0H.Vizier catalog entry
  4. 1 2 3 4 Nespral, D.; et al. (2017). "Mass determination of K2-19b and K2-19c from radial velocities and transit timing variations". Astronomy and Astrophysics. 601 A128. arXiv:1604.01265. Bibcode:2017A&A...601A.128N. doi:10.1051/0004-6361/201628639. S2CID 55978628.
  5. 1 2 3 4 Sinukoff, Evan; et al. (2016). "Eleven Multiplanet Systems From K2 Campaigns 1 and 2 and the Masses of Two Hot Super-Earths". The Astrophysical Journal. 827 (1) 78. arXiv:1511.09213. Bibcode:2016ApJ...827...78S. doi:10.3847/0004-637X/827/1/78.
  6. 1 2 3 Skrutskie, Michael F.; et al. (1 February 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
  7. 1 2 Armstrong, David J.; et al. (2015). "One of the closest exoplanet pairs to the 3:2 mean motion resonance: K2-19b and c". Astronomy and Astrophysics. 582 A33. arXiv:1503.00692. Bibcode:2015A&A...582A..33A. doi:10.1051/0004-6361/201526008. S2CID 8463154.
  8. ↑ Barros, S. C. C.; et al. (2015). "Photodynamical mass determination of the multiplanetary system K2-19". Monthly Notices of the Royal Astronomical Society. 454 (4): 4267–4276. arXiv:1510.01047. Bibcode:2015MNRAS.454.4267B. doi:10.1093/mnras/stv2271.
  9. 1 2 3 Almenara, J. M.; et al. (2025). "A decade of transit photometry for K2-19: Revised system architecture". Astronomy & Astrophysics. 703 A167. arXiv:2510.01985. Bibcode:2025A&A...703A.167A. doi:10.1051/0004-6361/202556436.
  10. ↑ "K2-19". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-12-31.
  11. ↑ Foreman-Mackey, Daniel; et al. (2015). "A Systematic Search for Transiting Planets in the K2 Data". The Astrophysical Journal. 806 (2) 215. arXiv:1502.04715. Bibcode:2015ApJ...806..215F. doi:10.1088/0004-637X/806/2/215.
  12. ↑ Montet, Benjamin T.; et al. (2015). "Stellar and Planetary Properties of K2 Campaign 1 Candidates and Validation of 17 Planets, Including a Planet Receiving Earth-like Insolation". The Astrophysical Journal. 809 (1) 25. arXiv:1503.07866. Bibcode:2015ApJ...809...25M. doi:10.1088/0004-637X/809/1/25.
  13. ↑ Vanderburg, Andrew; et al. (2016). "Planetary Candidates from the First Year of the K2 Mission". The Astrophysical Journal Supplement Series. 222 (1) 14. arXiv:1511.07820. Bibcode:2016ApJS..222...14V. doi:10.3847/0067-0049/222/1/14.
  14. ↑ Petigura, Erik A.; et al. (January 2020). "K2-19b and c are in a 3:2 Commensurability but out of Resonance: A Challenge to Planet Assembly by Convergent Migration". The Astronomical Journal. 159 (1) 2. arXiv:1910.12899. Bibcode:2020AJ....159....2P. doi:10.3847/1538-3881/ab5220.
  15. ↑ Petit, Antoine C; Petigura, Erik A; Davies, Melvyn B; Johansen, Anders (2020-08-11). "Resonance in the K2-19 system is at odds with its high reported eccentricities". Monthly Notices of the Royal Astronomical Society. 496 (3): 3101–3111. arXiv:2003.04931. Bibcode:2020MNRAS.496.3101P. doi:10.1093/mnras/staa1736.
  16. ↑ Williams, David R. (2018-09-27). "Mercury Fact Sheet". NASA. Retrieved 2019-01-12.
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