A team of astronomers have announced that they may have spotted the first evidence of a moon orbiting an exoplanet. The planet in question orbits the star Kepler-1625, about 4,000 light-years away, and is about the size of Jupiter. The planet dubbed Kepler-1625b is a lot denser at 10 times Jupiter’s mass. The moon? It’s about the size and mass of Neptune.
The team led by Dr. David Kipping, assistant professor of astronomy at Columbia University, detected the exomoon candidate using data from the Hubble Space Telescope and published their findings in a paper on Arvix.org. A synopsis for the paper said, “Exomoons represent an outstanding challenge in modern astronomy, with the potential to provide rich insights into planet formation theory and habitability.”
Most exoplanets are discovered through the detection of dips in the amount of a star’s light that reaches the observing telescope, which might indicate the transit of a planet. Exoplanet candidates are often observed for up to a few years, depending on their probable orbital period – i.e. the planet’s “year.” Exomoons would be detected in a similar way, by detecting variations in the amount of light that is reflected off a known exoplanet. Dr. Kipping’s team had detected three of these dips in the amount of light that Kepler-1625 reflects.
Dr. Kipping gave the observational data a confidence rating of 4 sigma, signifying that it could have been a fluke. As it appears from Earth, Kepler-1625 is pretty dim to begin with and the dip in the reflected light could have had another cause. That’s why they call it an exomoon candidate – the astronomical community has not yet confirmed that there is a moon orbiting that planet. The Hubble Space Telescope is expected to continue observations that could help confirm or rebuff Dr. Kipping’s findings.
If confirmed, the exomoon will be the largest moon ever discovered and could even help astronomers refine their theories about planetary formation. It could also help astronomers refine their approach to discovering exomoons, including ones that could be the size of Earth’s Moon.