An artist’s illustration of the exoplanet Kepler-1625b with its hypothesised moon, which is thought to be about the size of Neptune. Image credit: Dan Durda
The first serious exomoon candidate is likely the captured core of a baby giant planet, if the exotic world does indeed exist, a new study suggests.
In October 2018, Columbia University astronomers Alex Teachey and David Kipping announced that they’d spotted evidence of a Neptune-size world circling Kepler-1625b, a huge alien planet that lies about 8,000 light years from Earth.
This was big news: If confirmed, the newfound world, known as Kepler-1625b-i, would be the first moon ever discovered beyond our solar system. But confirmation has proven difficult.
Teachey and Kipping stressed at the time that the detection, made using observations by NASA’s Kepler and Hubble space telescopes, was tentative. Another research team has since argued against Kepler-1625b-i’s existence, and yet another one has stressed that the data are inconclusive at this point. So, one year later, Kepler-1625b-i remains a candidate rather than a bona fide world.
That status hasn’t stopped other scientists from trying to understand how the potential exomoon came to be, however. Indeed, a new study tackled that question and came up ...