Kepler-1625

Kepler-1625 is a 14th-magnitude solar-mass star located in the constellation of Cygnus approximately 8,000 light years away. Its mass is within 5% of that of the Sun, but its radius is approximately 70% larger reflecting its more evolved state. A candidate gas giant exoplanet was detected by the Kepler Mission around the star in 2015,[6] which was later validated as a likely real planet to >99% confidence in 2016.[7] In 2018, the Hunt for Exomoons with Kepler project reported that this exoplanet has evidence for a Neptune-sized exomoon around it, based on observations from NASA’s Kepler Mission.[8] Subsequent observations by the larger Hubble Space Telescope provided compounding evidence for a Neptune-sized satellite, with an on-going debate about the reality of this candidate signal.[9][10][11]

Kepler-1625
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cygnus
Right ascension  19h 41m 43.0402s[1]
Declination 39° 53′ 11.4990″[1]
Characteristics
Apparent magnitude (K) 13.916[2]
Astrometry
Proper motion (μ) RA: −2.145±0.064[1] mas/yr
Dec.: −4.799±0.068[1] mas/yr
Parallax (π)0.4065 ± 0.0358[1] mas
Distance8,000 ± 700 ly
(2,500 ± 200 pc)
Details
Mass1.04±0.08[3] M☉
Radius1.73±0.24[3] R☉
Luminosity (bolometric)2.57±0.68[3] L☉
Surface gravity (log g)3.99±0.10[3] cgs
Temperature5563±86[3] K
Metallicity [Fe/H]0.06±0.13[3] dex
Age8.7±2.1[3] Gyr
Other designations
KIC 4760478, KOI 5084, 2MASS J19414304+3953115
Database references
SIMBADdata
Data sources:
[4][5]

Stellar characteristics

Kepler-1625 is an approximately solar-mass star and yet is 1.7 times larger in diameter.[3] Its effective temperature is around 5,550 K, slightly lower than that of the Sun.[12][3] These parameters suggest that Kepler-1625 may be a yellow subgiant nearing the end of its life, with an age of approximately 8.7 billion years.[3] The star has been observed to be photometrically quiet, with periodic variability below 0.02%.[11] Kepler-1625 is located approximately 8,000 light-years away[1] in the constellation Cygnus.[12]

Planetary system
The Kepler-1625 planetary system[3]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b unknown M⊕ 0.86-1.12 287.3728±0.0022 — 89.97±0.02° 11.4±1.6 R⊕

The star is known to have one validated planet. Designated Kepler-1625b, it is a Jovian-sized planet orbiting its star every 287.3 Earth days. No other candidate transiting planets have been found around the star.[11]

Potential exomoon
Artist's impression of Kepler-1625b and its possible Neptune-sized moon

The Kepler Mission recorded three planetary transits of Kepler-1625b from 2009 to 2013.[6] From these, anomalous out-of-transit flux decrements indicated the possible existence of a Neptune-sized exomoon, as first reported by the Hunt for Exomoons with Kepler project in 2018.[8] The Kepler data were inconclusive and so the planetary transit was re-observed by the Hubble Space Telescope in October 2018. The light curve from Hubble exhibited evidence for both a moon-like transit and a Transit Timing Variation, both of which were consistent as being caused by the same Neptune-sized moon in orbit of Kepler-1625b.[3] The transit timing variation has been independently recovered by two teams analyzing the same data.[9][10] One of these teams also independently recovered the moon-like transit, but suggest that radial velocity measurements are needed to exclude the possibility of a close-in masquerading planet.[9] The other team are unable to recover the moon-like transit and suggested it may be an artifact of the data reduction.[10] This conclusion was challenged by the original team soon after, who showed that the other analysis exhibits larger systematics that may explain their differing conclusion.[11]

  • Relative size and distance of Kepler-1625b and its moon Kepler-1625b-I (Planets Jupiter and Neptune are shown for comparison)
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See also

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  2. "NASA Exoplanet archive". Retrieved 2017-07-28.
  3. Teachey, Alex; Kipping, David M. (2018). "Evidence for a Large Exomoon Orbiting Kepler-1625b" (PDF). Science Advances. 4 (10): eaav1784. arXiv:1810.02362. Bibcode:2018SciA....4.1784T. doi:10.1126/sciadv.aav1784. PMC 6170104. PMID 30306135. Retrieved 2019-04-25.
  4. NASA Exoplanet Archive, entry for Kepler-1625
  5. exoplanet.eu: Planet Kepler-1625 b
  6. Mullally, Fergus; et al. (2015). "Planetary Candidates Observed by Kepler. VI. Planet Sample from Q1--Q16 (47 Months)". The Astrophysical Journal. 217 (2). 31. arXiv:1502.02038. Bibcode:2015ApJS..217...31M. doi:10.1088/0067-0049/217/2/31.
  7. Morton, Timothy D.; et al. (2016). "False Positive Probabilities for all Kepler Objects of Interest: 1284 Newly Validated Planets and 428 Likely False Positives". The Astrophysical Journal. 822 (2). 86. arXiv:1605.02825. Bibcode:2016ApJ...822...86M. doi:10.3847/0004-637X/822/2/86.
  8. Teachey, Alex; et al. (2018). "HEK VI: On the Dearth of Galilean Analogs in Kepler and the Exomoon Candidate Kepler-1625b I". The Astronomical Journal. 155 (1). 36. arXiv:1707.08563. Bibcode:2018AJ....155...36T. doi:10.3847/1538-3881/aa93f2.
  9. Heller, Rene; Rodenbeck, Kai; Giovanni, Bruno (2019). "An alternative interpretation of the exomoon candidate signal in the combined Kepler and Hubble data of Kepler-1625". Astronomy and Astrophysics. 624: 95. arXiv:1902.06018. Bibcode:2019A&A...624A..95H. doi:10.1051/0004-6361/201834913.
  10. Kreidberg, Laura; Luger, Rodrigo; Bedell, Megan (2019-04-24). "No Evidence for Lunar Transit in New Analysis of HST Observations of the Kepler-1625 System". arXiv:1904.10618.
  11. Teachey, Alex; Kipping, David M.; Burke, Christopher (2019). "Loose Ends for the Exomoon Candidate Host Kepler-1625b". The Astronomical Journal. 159 (4): 142. arXiv:1904.11896. Bibcode:2020AJ....159..142T. doi:10.3847/1538-3881/ab7001.
  12. Mathur, Savita; Huber, Daniel; Batalha, Natalie M.; Ciardi, David R.; Bastien, Fabienne A.; Bieryla, Allyson; Buchhave, Lars A.; Cochran, William D.; Endl, Michael; Esquerdo, Gilbert A.; Furlan, Elise; Howard, Andrew; Howell, Steve B.; Isaacson, Howard; Latham, David W.; MacQueen, Phillip J.; Silva, David R. (2017). "Revised Stellar Properties of Kepler Targets for the Q1-17 (DR25) Transit Detection Run". The Astrophysical Journal Supplement Series. 229 (2): 30. arXiv:1609.04128. Bibcode:2017ApJS..229...30M. doi:10.3847/1538-4365/229/2/30.

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