Kepler-1625b I is a possible

moon The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

Kepler-1625b, which may be the first exomoon ever discovered (pending confirmation), and was first indicated after preliminary observations by the

Kepler Space Telescope The Kepler space telescope is a defunct space telescope launched by NASA in 2009 to discover Earth-sized planets orbiting other stars. Named after astronomer Johannes Kepler, the spacecraft was launched into an Earth-trailing heliocentric orb ...

. A more thorough observing campaign by the

Hubble Space Telescope The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...

took place in October 2017, ultimately leading to a discovery paper published in ''

Science Advances ''Science Advances'' is a peer-reviewed multidisciplinary open-access scientific journal established in early 2015 and published by the American Association for the Advancement of Science. The journal's scope includes all areas of science. Hist ...

'' 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 Neptune is the eighth and farthest known planet from the Sun. It is the List of Solar System objects by size, fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 t ...

. Like several moons in the Solar System, the large exomoon would theoretically be able to host its own moon, called a

subsatellite A subsatellite, also known as a submoon or informally a moonmoon, is a "moon of a moon" or a hypothetical natural satellite that orbits the moon of a planet. It is inference, inferred from the empirical study of natural satellites in the Solar S ...

, in a stable orbit, although no evidence for such a subsatellite has been found. Kepler-1625b and Bb distances

Studies and observations

The original paper presented two independent lines of evidence for the exomoon, a

transit timing variation Transit-timing variation is a method for detecting exoplanets by observing variations in the timing of a transit method, transit. This provides an extremely sensitive method capable of detecting additional planets in the system with masses potent ...

indicating a Neptune-mass moon, and a photometric dip indicating a Neptune-radius moon. An independent re-analysis of the observations published in February 2019 recovered both but suggested that an inclined and hidden hot-Jupiter could also be responsible, which could be tested with future

Doppler spectroscopy Doppler spectroscopy (also known as the radial-velocity method, or colloquially, the wobble method) is an indirect method for finding extrasolar planets and brown dwarfs from radial-velocity measurements via observation of Doppler shifts in ...

radial velocity observations. A third study analyzing this data set recovered the transit timing variation signature but not the photometric dip, and thus questioned the exomoon hypothesis. The original discovery team later addressed this paper, finding that their re-reduction exhibits higher systematics that may explain their differing conclusions.

References

{{portal bar, Astronomy, Space Exomoons

Studies and observations

See also

References