There are more than 200 moons in our Solar System, but their relatively small sizes make similarly sized extrasolar moons (exomoons) very hard to detect with current instruments. The best exomoon candidates so far are two nearly Neptune-sized bodies orbiting the Jupiter-sized exoplanets Kepler-1625b and Kepler-1708b, but their existence has been contested. In new research, astronomers reanalyzed the Hubble and Kepler data used to identify these two exomoon candidates.
From the discovery of Jupiter’s four principal moons in 1610 by Galileo Galilei, which triggered the Copernican revolution, to the discovery of cryovolcanism on Saturn’s moon Enceladus as evidence of continuing liquid water-based chemistry in the outer Solar System, moons continue to deliver fundamental and fascinating insights into planetary science.
The detection of moons around some of the thousands of extrasolar planets known today has, thus, been eagerly anticipated for over a decade now.
So far, two possible exomoon detections have been put forward, both of which had originally been claimed in data from NASA’s Kepler space mission.
The first candidate corresponds to a Neptune-sized moon in a wide orbit around the Jupiter-sized planet Kepler-1625b, which is in a 287-day orbit around the evolved solar-type star Kepler-1625.
The second exomoon claim has recently been announced by the same team. It is around the Jupiter-sized planet Kepler-1708b, which is in a 737-day orbit around the solar-type main-sequence star Kepler-1708.
“Exomoons are so far away that we cannot see them directly, even with the most powerful modern telescopes,” said Dr. René Heller, an astrophysicist at the Max Planck Institute for Solar System Research.
“Instead, telescopes record the fluctuations in brightness of distant stars, the time series of which is called a light curve.”
“Astronomers then look for signs of moons in these light curves. If an exoplanet passes in front of its star as seen from…
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