Last year, researchers revealed some tentative evidence that we had just discovered an exomoon. Now, new research strengthens the case and gives us a lot more information about this utterly peculiar potential exomoon.
As reported in Science, the system of Kepler-1625b is very similar to the Earth-Moon system in terms of mass-to-radius ratio, but scaled up 11 times. The planet could be up to three times more massive than Jupiter, which makes the candidate an exomoon, a truly unexpected object. It is roughly the size of Neptune.
The first hints that a moon could be orbiting this planet came from Kepler observations. There were anomalies that couldn’t be easily explained away. Two astronomers from Columbia University obtained 40 hours of telescope time on Hubble and were able to obtain four times better precision on the existing data. It also showed that the transit started 1.25 hours earlier than expected, and the explanation is that the moon was tugging at the planet. When these observations were tested against different hypotheses, the large moon idea was the winner.
“When we run our models, the moon model emerges as the best explanation for the data and has the added benefit for being a single explanation for the timing effects in the dimming of the star that we see in the data. Still, we are urging caution here,” lead author Alex Teachey said in a press conference.
“The first exomoon is obviously an extraordinary claim, and it requires extraordinary evidence. Furthermore, the size we have calculated for this moon, about the size of Neptune, has hardly been anticipated. That too is a reason to be careful here.”