BULLETIN
Exoplanet appears to have an unusually large satellite
New observations have found evidence of a moon the size of Neptune in orbit around an exoplanet. If confirmed, this will be the first time a moon has been discovered outside our Solar System.
The Kepler Space Telescope found the first signs of a moon in orbit around the 8,000 lightyears-distant exoplanet Kepler-1625b in 2017. A team of scientists investigated further using the Hubble Space Telescope, looking for dips in the host star’s brightness that could have been caused by the planet and moon passing in front of it. After first detecting the main planet’s transit, Hubble then spotted a second dip in brightness 3.5 hours later.
“A companion moon is the simplest and most natural explanation for the second dip,” said David Kipping, from Columbia University, who took part in the study. “It was definitely a shocking moment to see that light curve.”
The team also noted the planet’s transit occurred an hour earlier than expected. The presence of a moon could cause this, as it would pull the centre of gravity away from the core of the planet, causing it to wobble.
A second planet could be responsible for both these observations, but during Kepler’s four-year run it found no evidence of an additional planet around Kepler-1625.
The find will hopefully, “yield new insights into the development of planetary systems and may cause astronomers to revisit theories of how moons form,” according to Alex Teachey, the Columbia University graduate student who led the observations.
See Comment, right