Astronomy:Kepler-68
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.[1] The third planet has a mass similar to Jupiter but orbits within the habitable zone.[2]
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 showed that the companion's proper motion appeared consistent with it being bound to the Kepler-68 system, but further observations were needed to confirm this conclusion.[3] In 2019 this was found to be an unrelated background star using Gaia DR2 astrometry.[4]
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.[2][5] 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.[6] In 2023, this fourth planet was confirmed, with a minimum mass about that of Saturn.[1]
| 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
- ↑ 1.0 1.1 1.2 Bonomo, A. S. 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. doi:10.1051/0004-6361/202346211. Bibcode: 2023A&A...677A..33B.
- ↑ 2.0 2.1 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. doi:10.1088/0004-637X/766/1/40. Bibcode: 2013ApJ...766...40G.
- ↑ 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. doi:10.1093/mnras/stw049. Bibcode: 2016MNRAS.457.2173G. https://academic.oup.com/mnras/article/457/2/2173/968721.
- ↑ Mugrauer, M. (December 2019). "Search for stellar companions of exoplanet host stars by exploring the second ESA-Gaia data release". Monthly Notices of the Royal Astronomical Society 490 (4): 5088–5102. doi:10.1093/mnras/stz2673. Bibcode: 2019MNRAS.490.5088M.
- ↑ 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. doi:10.1088/0067-0049/210/2/20. Bibcode: 2014ApJS..210...20M.
- ↑ Mills, Sean M. et al. (2019). "Long-period Giant Companions to Three Compact, Multiplanet Systems". The Astronomical Journal 157 (4): 145. doi:10.3847/1538-3881/ab0899. Bibcode: 2019AJ....157..145M.
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