Kepler-68
Observation data
Epoch J2000      Equinox J2000
Constellation Cygnus
Right ascension 19h 24m 07.76597s[1]
Declination +49° 02′ 24.9283″[1]
Apparent magnitude (V) 10.08[2]
Characteristics
Evolutionary stage Main sequence
Spectral type G1V
Astrometry
Radial velocity (Rv)−20.50±0.23[1] km/s
Proper motion (μ) RA: −7.305 mas/yr[1]
Dec.: −10.454 mas/yr[1]
Parallax (π)6.9298 ± 0.0100 mas[1]
Distance470.7 ± 0.7 ly
(144.3 ± 0.2 pc)
Details[3]
Mass1.057+0.022
−0.020 M☉
Radius1.2564±0.0084 R☉
Temperature5847±75 K
Metallicity [Fe/H]0.11±0.06 dex
Rotational velocity (v sin i)2.4±0.5[4] km/s
Age6.84+0.90
−1.04 Gyr
Other designations
BD+48 2893, KOI-246, KIC 11295426, TYC 3551-189-1, GSC 03551-00189, 2MASS J19240775+4902249[4]
Database references
SIMBADdata
KICdata

Kepler-68 is a Sun-like main sequence star located 471 light-years (144 parsecs) away in the constellation Cygnus. It is known to have at least four planets orbiting around it.[3] The third planet has a mass similar to Jupiter but orbits within the habitable zone.[5]

High resolution imaging observations of Kepler-68 carried out with the lucky imaging instrument AstraLux on the 2.2m telescope at Calar Alto Observatory detected a wide companion candidate approximately 11 arcseconds away. Comparing these observations to the 2MASS positions shows that the companions proper motion is consistent with it being bound to the Kepler-68 system, but further observations are needed to confirm this conclusion.[6] Eleven arcseconds at the distance of Kepler-68 leads to a sky projected separation of approximately 1600 Astronomical units. A circular orbit at that distance would have a period of roughly 50,000 years.[7]

Planetary system

Currently, four planets have been discovered to orbit around Kepler-68. The two innermost planets were discovered by the planetary transit method. Follow-up Doppler measurements helped to determine the mass of Kepler-68b and helped to discover Kepler-68d.[5][8] There is an additional signal present in the radial velocity measurements indicating another body in the system at a period of greater than 10 years. The mass of this object was initially unknown and it could be either another planet or a stellar companion.[7] In 2023, this fourth planet was confirmed, with a minimum mass about that of Saturn.[3]

The Kepler-68 planetary system[3]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b 8.03±0.67 M🜨 0.06135±0.00043 5.39875259 <0.090 87.23+0.22
−0.17° 		2.357±0.023 R🜨
c <1.3 M🜨 0.09008±0.00063 9.605027 <0.099 87.071+0.087
−0.094° 		0.979±0.019 R🜨
d ≥0.749±0.017 MJ 1.469±0.010 632.62±1.03 0.102±0.016 — —
e ≥0.272±0.032 MJ 4.60+0.32
−0.16 		3455+348
−169 		0.33±0.11 — —

References

  1. ^ a b c d e 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.
  2. ^ Høg, E. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H.
  3. ^ a b c d Bonomo, A. S.; Dumusque, X.; et al. (April 2023). "Cold Jupiters and improved masses in 38 Kepler and K2 small-planet systems from 3661 high-precision HARPS-N radial velocities. No excess of cold Jupiters in small-planet systems". Astronomy & Astrophysics. arXiv:2304.05773. doi:10.1051/0004-6361/202346211. S2CID 258078829.
  4. ^ a b "Kepler-68". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-10-16.
  5. ^ a b Gilliland, Ronald L.; et al. (2013). "Kepler-68: Three Planets, One with a Density Between That of Earth and Ice Giants". The Astrophysical Journal. 766 (1). 40. arXiv:1302.2596. Bibcode:2013ApJ...766...40G. doi:10.1088/0004-637X/766/1/40.
  6. ^ Ginski, C.; et al. (2016). "A lucky imaging multiplicity study of exoplanet host stars – II". Monthly Notices of the Royal Astronomical Society. 457 (2): 2173–2191. arXiv:1601.01524. Bibcode:2016MNRAS.457.2173G. doi:10.1093/mnras/stw049.
  7. ^ a b Mills, Sean M.; et al. (2019). "Long-period Giant Companions to Three Compact, Multiplanet Systems". The Astronomical Journal. 157 (4). 145. arXiv:1903.07186. Bibcode:2019AJ....157..145M. doi:10.3847/1538-3881/ab0899. S2CID 119197547.
  8. ^ Marcy, Geoffrey W.; et al. (2014). "Masses, Radii, and Orbits of Small Kepler Planets: The Transition from Gaseous to Rocky Planets". The Astrophysical Journal Supplement Series. 210 (2). 20. arXiv:1401.4195. Bibcode:2014ApJS..210...20M. doi:10.1088/0067-0049/210/2/20.
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