Kepler-1708b I is an exomoon candidate that may orbit around the

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...

Kepler-1708b, which is located about 5500

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 1012 ...

s from the Solar System. Notations such as Kepler 1708b-i can also be seen. Kepler-1708b I is the second exomoon candidate, after

Kepler-1625b I Kepler 1625b I, a possible moon of exoplanet Kepler-1625b, may be the first exomoon ever discovered (pending confirmation), and was first indicated after preliminary observations by the Kepler Space Telescope. A more thorough observing campaign ...

Discovery

A survey of 70 cooler giant planets potentially hosting exomoons, discovered by the

Kepler space telescope The Kepler space telescope is a disused 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 ...

through observation of transits, was conducted; only Kepler-1708b was named as a candidate for having satellites. A paper reporting the possible discovery of Kepler-1708b I was submitted to arXiv on January 12, 2022. The false positive rate for Kepler-1708b I is only about 1%, with an even lower probability that the alleged satellite signal may be due to an unknown exoplanet other than Kepler-1708b orbiting around Kepler-1708. Although there is no evidence that Kepler-1708b I is not an exomoon at this time, it is still in the candidate stage, and future follow-up observations are required to confirm its existence. Additional Kepler-1708b I transit observations and transit-timing variations may be observable if future observations are made by the

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

James Webb Space Telescope The James Webb Space Telescope (JWST) is a space telescope which conducts infrared astronomy. As the largest optical telescope in space, its high resolution and sensitivity allow it to view objects too old, distant, or faint for the Hubble Spa ...

, PLATO, etc. The last transit occurred on March 24, 2023.

Characteristics

Kepler-1708b I is said to be a

mini-Neptune A Mini-Neptune (sometimes known as a gas dwarf or transitional planet) is a planet less massive than Neptune but resembling Neptune in that it has a thick hydrogen–helium atmosphere, probably with deep layers of ice, rock or liquid oceans (made ...

or possibly a super-Earth with a radius of about 2.6

Earth radii Earth radius (denoted as ''R''🜨 or R_E) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid, the radius ranges from a maximum of nearly (equatorial radius, deno ...

. This is a much smaller size than Kepler-1625b I. Kepler-1708b I orbits at a distance of 740,000 kilometres from Kepler-1708b, with a period of about 4.6 days, in the same plane as the planet's orbit around the star.

References

{{2022 in space Exomoons

Discovery

Characteristics

See also

References