Kepler-1625b I

{{use dmy dates|date = October 2018}}

{{short description|Possible exomoon orbiting Kepler-1625b in the constellation of Cygnus}}

{{Infobox planet

|extrasolarplanet = yes

|name = Kepler-1625b I

|image = File:Exomoon Kepler-1625b-I orbiting its planet (artist’s impression).tiff

|image_scale =

|image_alt =

|caption = Exomoon Kepler-1625b I orbiting exoplanet Kepler-1625b (artist concept).{{cite web|last1 = Chou|first1 = Felicia|last2 = Villard|first2 = Ray|last3 = Hawkes|first3 = Alison|last4 = Brown|first4 = Katherine|title = Astronomers Find First Evidence of Possible Moon Outside Our Solar System|url = https://www.nasa.gov/press-release/astronomers-find-first-evidence-of-possible-moon-outside-our-solar-system/|date = 3 October 2018|work = NASA|access-date = 5 October 2018}}

|apsis = astron

|discovery_ref = {{cite journal|title = Evidence for a large exomoon orbiting Kepler-1625b|last1 = Teachey|first1 = Alex|last2 = Kipping|first2 = David M.|display-authors = 1|journal = Science Advances|volume = 4|issue = 10|year = 2018|doi = 10.1126/sciadv.aav1784|pmid = 30306135|pmc = 6170104|page = eaav1784|arxiv = 1810.02362|bibcode = 2018SciA....4.1784T }}

|discoverer = Alex Teachey, David M. Kipping and Allan R. Schmitt

|discovery_site =

|discovered = 2017

|discovery_method = Primary transit

|alt_names =

|periastron =

|apoastron =

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|avg_speed =

|eccentricity =

|period =

|inclination =

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|semi-amplitude =

|mean_radius = 0.437 R_J

|surface_area =

|volume =

|density = 0.95 g/cm³

|mass = 19.069 M_🜨
0.06 M_J{{cite encyclopedia|url = http://exoplanet.eu/catalog/kepler-1625_b_i/|title = The Extrasolar Planet Encyclopaedia — Kepler-1625 b I|access-date = 7 October 2018|archive-date = 5 October 2018|archive-url = https://web.archive.org/web/20181005072053/http://exoplanet.eu/catalog/kepler-1625_b_i/|encyclopedia = Extrasolar Planets Encyclopaedia|url-status = dead}}

|surface_grav =

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|satellite_of = Kepler-1625b

}}

Kepler-1625b I is a possible moon of exoplanet Kepler-1625b, which may be the first exomoon ever discovered (pending confirmation), and was first indicated after preliminary observations by the Kepler Space Telescope.{{Cite journal|last1 = Teachey|first1 = A.|last2 = Kipping|first2 = D. M.|last3 = Schmitt|first3 = A. R.|date = 26 July 2017|title = HEK. VI. On the Dearth of Galilean Analogs in Kepler, and the Exomoon Candidate Kepler-1625b I|journal = The Astronomical Journal|publication-date = 22 December 2017|volume = 155|issue = 1|page = 36|arxiv = 1707.08563|bibcode = 2018AJ....155...36T|doi = 10.3847/1538-3881/aa93f2|s2cid = 118911978 | doi-access=free }} A more thorough observing campaign by the Hubble Space Telescope took place in October 2017, ultimately leading to a discovery paper published in Science Advances in early October 2018. Studies related to the discovery of this moon suggest that the host exoplanet is up to several Jupiter masses in size, and the moon is thought to be approximately the mass of Neptune. Like several moons in the Solar System,{{cite journal|last1 = Kollmeier|first1 = Juna A.|last2 = Raymond|first2 = Sean N.|date = 21 November 2018|title = Can moons have moons?|url = https://academic.oup.com/mnrasl/article/483/1/L80/5195537|journal = Monthly Notices of the Royal Astronomical Society: Letters|volume = 483|pages = L80–L84|arxiv = 1810.03304|doi = 10.1093/mnrasl/sly219| doi-access=free }} the large exomoon would theoretically be able to host its own moon, called a subsatellite, in a stable orbit, although no evidence for such a subsatellite has been found.{{Cite journal|last = Forgan|first = Duncan H.|date = 11 February 2019|title = The habitable zone for Earth-like exomoons orbiting Kepler-1625b|url = https://www.cambridge.org/core/journals/international-journal-of-astrobiology/article/abs/habitable-zone-for-earthlike-exomoons-orbiting-kepler1625b/D8A5CEB8416914F2CD0D9B275F4E8FBB|journal = International Journal of Astrobiology|volume = 18|issue = 6|pages = 510–517|arxiv = 1810.02712|doi = 10.1017/s1473550418000514| bibcode=2019IJAsB..18..510F | s2cid=118857039 |issn = 1473-5504}}

File:Kepler-1625b and Bb distances.jpg and its moon Kepler-1625b-I, using images of Jupiter and Neptune]]