Observation data
Epoch J2000      Equinox
Constellation Cygnus
Right ascension 19h 18m 57.5312s
Declination +44° 38′ 50.6176″
Radial velocity (Rv)-35.16[1] km/s
Proper motion (μ) RA: 3.216[1] mas/yr
Dec.: -10.925[1] mas/yr
Parallax (π)1.7436 ± 0.0666[1] mas
Distance1,870 ± 70 ly
(570 ± 20 pc)
Position (relative to KOI-5A)[2]
Epoch of observation2016
Angular distance0.029±0.050
Position angle142.1±1.0°
Observed separation
16[citation needed] AU
Position (relative to KOI-5A)[2]
Epoch of observation2016
Angular distance0.141±0.050
Position angle304.3±2.2°
Observed separation
78[citation needed] AU
Mass1.13[4] M
Radius1.840±0.017 R
Luminosity3.86±0.17 L
Surface gravity (log g)4.19[5] cgs
Temperature5861[5] K
Age3.49±0.41 Gyr
Mass1.09[4] M
Other designations
TOI-1241, 2MASS J19185753+4438507, KIC 8554498, Gaia EDR3 2126945668448657664
Database references

KOI-5 is a triple star system composed of three stars: KOI-5 A, KOI-5 B and KOI-5 C, orbiting 1,870±70 light-years away.

The two dim stellar companions to KOI-5A were discovered in 2016.[2] KOI-5 A and B orbit each other every 29 years, and KOI-5 C orbits stars A and B every 400 years.[4] KOI-5C is physically associated with the core stellar pair with probability 99.98%.[6]

Planetary system

The two planets orbiting one of KOI-5's stars were suspected since 2009 based on Kepler data, but KOI-5Ab was confirmed only in January 2021 after TESS determined the planet is orbiting KOI-5A. The exoplanet has caused interest in the scientific community because its orbital plane is misaligned with the closer star, suggesting it gave KOI-5Ab a gravitational kick during its development, resulting in the misalignment and inward migration to the current orbit.[4] Planet c may be a false positive.[7]

The KOI-5A planetary system[6][4]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
c (unconfirmed) 0.075[7] 7.05185637[7] 0.66 R
b 0.179 MJ 0.0596060 5 7.07 R🜨


  1. ^ a b c d Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. Gaia EDR3 record for this source at VizieR.
  2. ^ a b c Furlan, E.; Ciardi, D. R.; Everett, M. E.; Saylors, M.; Teske, J. K.; Horch, E. P.; Howell, S. B.; Van Belle, G. T.; Hirsch, L. A.; Gautier, T. N.; Adams, E. R.; Barrado, D.; Cartier, K. M. S.; Dressing, C. D.; Dupree, A. K.; Gilliland, R. L.; Lillo-Box, J.; Lucas, P. W.; Wang, J. (2017), "The Kepler Follow-Up Observation Program. I. A Catalog of Companions To Kepler Stars from High-Resolution Imaging", The Astronomical Journal, 153 (2): 71, arXiv:1612.02392, Bibcode:2017AJ....153...71F, doi:10.3847/1538-3881/153/2/71, S2CID 38339900
  3. ^ Bellinger, E. P.; Hekker, S.; Angelou, G. C.; Stokholm, A.; Basu, S. (2020), "Stellar ages, masses, and radii from asteroseismic modeling are robust to systematic errors in spectroscopy", Astronomy & Astrophysics, 622: A130, arXiv:1812.06979, doi:10.1051/0004-6361/201834461, S2CID 119293351
  5. ^ a b Batalha, Natalie M.; Rowe, Jason F.; Bryson, Stephen T.; Barclay, Thomas; Burke, Christopher J.; Caldwell, Douglas A.; Christiansen, Jessie L.; Mullally, Fergal; Thompson, Susan E.; Brown, Timothy M.; Dupree, Andrea K.; Fabrycky, Daniel C.; Ford, Eric B.; Fortney, Jonathan J.; Gilliland, Ronald L.; Isaacson, Howard; Latham, David W.; Marcy, Geoffrey W.; Quinn, Samuel N.; Ragozzine, Darin; Shporer, Avi; Borucki, William J.; Ciardi, David R.; Gautier, Thomas N.; Haas, Michael R.; Jenkins, Jon M.; Koch, David G.; Lissauer, Jack J.; Rapin, William; et al. (2013), "Planetary Candidates Observed by Kepler . III. Analysis of the First 16 Months of Data", The Astrophysical Journal Supplement Series, 204 (2): 24, arXiv:1202.5852, Bibcode:2013ApJS..204...24B, doi:10.1088/0067-0049/204/2/24, S2CID 19023502
  6. ^ a b Hirsch, Lea A.; Ciardi, David R.; Howard, Andrew W.; Everett, Mark E.; Furlan, Elise; Saylors, Mindy; Horch, Elliott P.; Howell, Steve B.; Teske, Johanna; Marcy, Geoffrey W. (2017), "Assessing the Effect of Stellar Companions from High-resolution Imaging of Kepler Objects of Interest", The Astronomical Journal, 153 (3): 117, arXiv:1701.06577, Bibcode:2017AJ....153..117H, doi:10.3847/1538-3881/153/3/117, S2CID 39321033
  7. ^ a b c "Exoplanet Archive". exoplanetarchive.ipac.caltech.edu. Retrieved 2021-07-17.

Coordinates: Sky map 19h 18m 57.5312s, +44° 38′ 50.6176″