A team of astronomers led by David Kipping, from Columbia University, announced in 2017 that they may have discovered the very first extrasolar moon, or exomoon. Follow-up operations with Hubble now seem to confirm its existence, 8,000 light-years away. The details of the study are reported in the journal Science Advances.
Thousands of exoplanets have been discovered so far, most thanks to the transit method – a planet passes its star and blocks some of its emitted light. But until now, and quite logically, no extrasolar moon was detected with this method, brightness variations being insignificant. But it was without counting on human instrumentation. Follow-up observations made with Hubble now seem to confirm Kepler’s suspicions: there would be an exomoon – Kepler-1625b-i – 8,000 light-years away from Earth.
“This would be the first case of moon detection outside our solar system,” says David Kipping. If these observations are confirmed, the conclusions could provide essential clues about the development of planetary systems and lead experts to revisit theories of moon formation around planets.
Kepler-1625b-i evolves around a gas giant – Kepler-1625b – itself circling a yellow star similar to our Sun. And this gas moon would be huge: about the size of Neptune – and therefore larger than the Earth. It would gravitate about 3 million kilometers from its planet.
If these observations seem very conclusive, they are not 100% confirmed. These small variations in luminosity could also be explained by the presence of a second planet, and not a moon. But the researchers are confident.
“If this system is validated – a hot Jupiter with a moon the size of Neptune – it would be remarkable and endowed with unexpected properties,” the researcher continues. We look forward to a thorough review of this work by the scientific community, and hope that we will have the opportunity to observe the target again in a short time.”