Kepler-1625b

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Kepler-1625b
Kepler-1625b and Kepler-1625b I (artist's impression).png
Artist's impression of the exoplanet Kepler-1625b and its candidate exomoon Kepler-1625b I.
Discovery
Discovery site Kepler Space Observatory
Discovery dateMay 10, 2016
Transit (Kepler Mission)
Orbital characteristics [1]
0.98 ± 0.14 AU
287.378949 d
Inclination 89.97 ± 0.02
Known satellites Kepler-1625b I?
Star Kepler-1625
Physical characteristics
1.18+0.18
−0.32  RJ [2]
Mass ≤11.60 MJ [3]

    Kepler-1625b is a super-Jupiter exoplanet orbiting the Sun-like star Kepler-1625 about 2,500 parsecs (8,200 light-years ) away in the constellation of Cygnus. [4] The large gas giant is approximately the same radius as Jupiter, [1] and orbits its star every 287.4 days. [5] In 2017, hints of a Neptune-sized exomoon in orbit of the planet were found using photometric observations collected by the Kepler Mission. [6] [7] Further evidence for a Neptunian moon was found the following year using the Hubble Space Telescope, where two independent lines of evidence constrained the mass and radius to be Neptune-like. [1] The mass-signature has been independently recovered by two other teams. [8] [9] However, the radius-signature was independently recovered by one of the teams [9] but not the other. [8] The original discovery team later showed that this latter study appears affected by systematic error sources that may have influenced its findings. [10]

    Contents

    Characteristics

    Mass and radius

    Kepler-1625b is a Jovian-sized gas giant, a type of planet several times greater in radius than Earth and mostly composed of hydrogen and helium. It has been estimated to be 11.4±1.5 times Earth's radius, approximately equal to that of the planet Jupiter. [1] Its mass is unknown, but is constrained at 3-sigma confidence to be less than 11.6 times the mass of Jupiter (about 3,700 Earth masses), based on non-detection in radial velocity observations. [3] This indicates that it is below the deuterium-fusing limit, which is around 13 Jupiter masses, and so it is not a brown dwarf. [3]

    Orbit and temperature

    Unlike the gas giants in our Solar System, Kepler-1625b orbits much closer, slightly closer than the orbital radius as the Earth around the Sun. [1] The planet takes 287 days (0.786 years ; 9.43 months ) to orbit Kepler-1625, as a result of the star's slightly greater mass than the Sun. Kepler-1625b receives 2.6 times more insolation than the Earth, [1] meaning it lies at the inner edge of the habitable zone. [11] However, as the planet has likely no solid surface, bodies of liquid water are impossible.

    Candidate exomoon

    In July 2017, researchers found signs of a Neptune-sized exomoon (a moon in another solar system) orbiting Kepler-1625b using archival Kepler Mission data. [6] [7]

    In October 2018, researchers using the Hubble Space Telescope published new observations of the star Kepler-1625 which revealed two independent lines of evidence indicative of a large exomoon Kepler-1625b I. [1] [12] These were a 20-minute Transit Timing Variation signature that indicated an approximately Neptune-mass moon, and an additional photometric dip that indicated a Neptune-radius moon. [1] The relative phasing of the two signatures was also consistent with that which a real moon would cause, with the effects in anti-phase. [1] The study concluded that the exomoon hypothesis is the simplest and best explanation for the available observations, though warned that it is difficult to assign a precise probability to its reality and urged follow-up analyses. [13] [1]

    In February 2019, a reanalysis of the combined Kepler and Hubble observations recovered both a moon-like dip and similar transit timing variation signal. [9] However, the authors suggested that the data could also be explained by an inclined hot-Jupiter in the same system that has gone previously undetected, which could be tested using future Doppler spectroscopy radial velocity measurements. A second independent reanalysis was published in April 2019, which recovered one of the two lines of evidence, the transit timing variation, but the not the second, the moon-like dip. [8] The original discovery team responded to this soon after, finding that this re-analysis exhibits stronger systematics in their reduction which may be responsible for their differing conclusion. [10]

    References

    1. 1 2 3 4 5 6 7 8 9 10 Teachey, Alex; et al. (October 3, 2018). "Evidence for a large exomoon orbiting Kepler-1625b". Science Advances. 4 (10) eaav1784. arXiv: 1810.02362 . Bibcode:2018SciA....4.1784T. doi:10.1126/sciadv.aav1784. PMC   6170104 . PMID   30306135.
    2. ↑ Heller, René (2018-02-01). "The nature of the giant exomoon candidate Kepler-1625 b-i". Astronomy & Astrophysics. 610: A39. doi:10.1051/0004-6361/201731760. ISSN   0004-6361.
    3. 1 2 3 Timmermann, Anina; Heller, Rene; Reiner, Ansgar; Zechmeister, Mathias (2020). "Radial velocity constraints on the long-period transiting planet Kepler-1625 b with CARMENES". Astronomy and Astrophysics. 635: 59. arXiv: 2001.10867 . Bibcode:2020A&A...635A..59T. doi:10.1051/0004-6361/201937325. S2CID   210942758.
    4. ↑ Luri, X.; Brown, A.; Sarro, L. (August 10, 2018). "Gaia Data Release 2". Astronomy & Astrophysics . 616: 19. arXiv: 1804.09376 . Bibcode:2018A&A...616A...9L. doi:10.1051/0004-6361/201832964. S2CID   244895570 . Retrieved April 1, 2022.
    5. ↑ "Exoplanet Exploration: Planets Beyond our Solar System". Exoplanet Exploration: Planets Beyond our Solar System. Archived from the original on October 3, 2018.
    6. 1 2 Crane, Leah (July 27, 2017). "First exomoon might have been spotted 4000 light years away". NewScientist. Retrieved April 1, 2022.
    7. 1 2 Teachey, Alex; et al. (December 22, 2017). "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 . S2CID   118911978.
    8. 1 2 3 Kreidberg, Laura; Luger, Rodrigo; Bedell, Megan (April 24, 2019). "No Evidence for Lunar Transit in New Analysis of Hubble Space Telescope Observations of the Kepler-1625 System". The Astrophysical Journal. 877 (2): L15. arXiv: 1904.10618 . Bibcode:2019ApJ...877L..15K. doi: 10.3847/2041-8213/ab20c8 . S2CID   129945202.
    9. 1 2 3 Heller, Rene; Rodenbeck, Kai; Giovanni, Bruno (April 17, 2019). "An alternative interpretation of the exomoon candidate signal in the combined Kepler and Hubble data of Kepler-1625". Astronomy & Astrophysics . 624. 8. arXiv: 1902.06018 . Bibcode:2019A&A...624A..95H. doi:10.1051/0004-6361/201834913. S2CID   119311103 . Retrieved April 1, 2022.
    10. 1 2 Teachey, Alex; Kipping, David M.; Burke, Christopher (March 5, 2020). "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 . S2CID   135465103.
    11. ↑ Zsom, Andras; Seager, Sara; et al. (2013). "Towards the Minimum Inner Edge Distance of the Habitable Zone". The Astrophysical Journal. 778 (2): 109. arXiv: 1304.3714 . Bibcode:2013ApJ...778..109Z. doi:10.1088/0004-637X/778/2/109. S2CID   27805994.
    12. ↑ "Kelpler-1625b-I". Extrasolar Planets Encyclopaedia . 15 July 2019. Archived from the original on 5 October 2018. Retrieved 14 December 2020.
    13. ↑ Drake, Nadia (3 October 2018). "Weird giant may be the first known alien moon - Evidence is mounting that a world the size of Neptune could be orbiting a giant planet far, far away". National Geographic Society . Archived from the original on October 3, 2018. Retrieved 4 October 2018.
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