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]
| 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] |
| Distance | 470.7 ± 0.7 ly (144.3 ± 0.2 pc) |
| Details[3] | |
| Mass | 1.057+0.022 −0.020 M☉ |
| Radius | 1.2564±0.0084 R☉ |
| Temperature | 5847±75 K |
| Metallicity [Fe/H] | 0.11±0.06 dex |
| Rotational velocity (v sin i) | 2.4±0.5[4] km/s |
| Age | 6.84+0.90 −1.04 Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
| KIC | data |
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
editCurrently, 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]
| 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
edit- ^ 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.
- ^ 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.
- ^ 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. 677. arXiv:2304.05773. Bibcode:2023A&A...677A..33B. doi:10.1051/0004-6361/202346211. S2CID 258078829.
- ^ a b "Kepler-68". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-10-16.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.