The first suspected exomoon is coming into focus. Observations with the Hubble Space Telescope bolster the case for a Neptune-sized moon orbiting a gas exoplanet 8,000 light-years away, astronomers report October 3 in Science Advances. The moon’s existence, if confirmed, would challenge theories of how satellites are born.
Astronomers David Kipping and Alex Teachey of Columbia University trained Hubble on the star Kepler 1625 for 40 hours on October 28 and 29, 2017. The star was known to have a Jupiter-sized planet orbiting it every 287 days, thanks to observations by the Kepler space telescope, which detects dips in starlight that indicate a planet is transiting in front of the star.