A research group has found evidence of an exo-moon near an exoplanet 5500 light-years away from us. It is only the second such candidate ever.
The team led by David Kipping from Columbia University discovered the telltale signals while searching 70 particularly promising exoplanets, they now explain. They only found one in one. The signal at Kepler-1708b was particularly persistent, which is why they are now presenting it publicly. However, it could still take a while for a possible confirmation. Kipping was responsible for the discovery of the first possible exomond as early as 2018, but it has not yet been verified whether Kepler-1625b-i is really an exomond.
Two and a half times the size of Earth
The now featured in the journal Nature Astronomy second exomond candidate Kepler-1708 bi is huge. It is two and a half times the size of Earth and orbits a gas planet that is itself about 1.6 times the size of Jupiter. The orbit corresponds to 12 radii of this planet. But these values are no coincidence, Kipping and his team have specifically looked at such gas giants.
In the solar system, too, the largest planets have by far the most moons, at the same time they assumed that the outliers would be found first: “The big ones, which are simply the easiest to find with our limited resources,” says Kipping. Kepler-1708 bi would have to be confirmed by targeted observations, for example with the Hubble space telescope, he now adds. That could take years.
The Kepler space telescope searched for exoplanets from 2009 to 2018 and is still by far the most successful instrument. The probe continuously observed thousands of stars, looking for small fluctuations in brightness. Except for those that were caused by passing objects, the space telescope. Kipping and his team searched Kepler’s data on the 70 exoplanets for particular dents in the light curves that indicated that not only a planet passed in front of the star, but also a moon. Given the difficulties in confirming the first potential exomond, Kepler-1708 bi still has a chance of becoming the first confirmed exomond.