Did Astronomers Just Discover A Neptune-Sized Exomoon Orbiting Kepler-1625b?

An international team of astronomers working on "The Hunt for Exomoons with Kepler" (HEK) project published a paper announcing the possibility that the first known moon outside our solar system has been detected.

The potential exomoon is supposedly about the size of Neptune and orbits the Jupiter-sized exoplanet, Kepler-1625b. The exomoon candidate is now called Kepler-1625b I, or by the team's nickname, Nep-moon.

How Was Nep-Moon Detected?

Using observations from the Kepler spacecraft, scientists are able to find exoplanet candidates by recording the number of instances the light from a distant star dims whenever a celestial body passes between it and the Earth. By extension, exomoons are detected by noting the instances of dimming of light reflected from an exoplanet as its moon transits.

The HEK team, led by Dr. David Kipping of Columbia University, noted three instances of Kepler 1625b dimming as Nep-Moon passed, which established an orbit.

So Is Nep-Moon Really An Exomoon?

We're talking about a celestial body in a star system that is roughly 4,000 light years away, so it's safe to say that Nep-Moon could be anything, really.

"[We] want to be crystal clear that we are not claiming a detection at this point," study co-author Alex Teachey states.

There has also been an exomoon candidate detection in 2014 but that could not be verified because it was only detected through a rare microlensing phenomenon. However, Nep-Moon was not detected when a rare phenomenon occurred and there were three instances of its transit that have been recorded so the HEK team assures that there are ways to verify its status.

In order to validate their find, the HEK team has already scheduled some time with the Hubble Space Telescope in October 2017 to get a better grasp of what Kepler-1625b I really is.

"We're excited about it... statistically, formally, it's a very high probability [but] until we get the measurements from Hubble, it may as well be 50-50 in my mind," Dr. Kipping said.

Other astronomers not involved with the study agree with that mindset and have opted to wait for more convincing evidence that the candidate could actually be an exomoon.

"Any time the word 'candidate' is in the [study] title, it is just that, a candidate. I am definitely looking forward to the Hubble Space Telescope observations in 2017 to see if anything is actually there," MIT professor of planetary science and physics Sara Seager expressed.

If Hubble is able to confirm Nep-Moon's status as an exomoon, one could only imagine grander discoveries that the European Southern Observatory's (ESO) Extremely Large Telescope (ELT) could validate when its construction is finished.

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