51����

That’s no moon. Evidence for what seemed to be the first moon ever discovered outside our solar system looks like it may actually just be a statistical blip. This is the second time the evidence for this exomoon has evaporated with a harder look at the data – and now we may never know if it really exists.

In 2017, 51���� reported that David Kipping and Alex Teachey at Columbia University in New York had spotted a possible exomoon orbiting a planet around the star Kepler-1625 in data from the Kepler Space Telescope. At the time, the researchers said the data was inconclusive and switched to the Hubble Space Telescope to take another look.

In the mean time, new analyses of the Kepler data cast questions on the conclusion. So when the Hubble observations seemed to spy the signal of a Neptune-sized exomoon, that became the only solid evidence. The data showed a dip in the star’s light as the planet passed between it and the telescope, and then another smaller dip attributed to the moon.

But according to a new analysis by Laura Kreidberg at the Harvard-Smithsonian Center for Astrophysics in Massachusetts and her colleagues, that evidence isn’t so solid after all. Kreidberg used the same raw data as Kipping and Teachey, but processed it separately.

“I tried my best to reproduce the exact steps that the original authors used, and I found that I couldn’t reproduce their result,” Kreidberg says. In her team’s data analysis, the extra dip in starlight was gone.

It’s not clear why: the two teams have each analysed each other’s work, and neither have found any specific step that would make the two different – it’s an astronomical stalemate.

“Neither team was able to identify anything the other team did wrong, says Kipping. “We can’t put our finger on anything that could cause the difference in these two analyses and that’s frustrating.”

Another finding that supported the exomoon hypothesis, the fact that the planet seems to be wobbling, remained solid in Kreidberg’s reanalysis. This kind of wobble is often caused by the gravitational tug of either a moon or a second planet.

At this point, we don’t know what is going on – and we might never know, because Kipping and Teachey’s request to observe Kepler-1625 with the Hubble telescope again in May was denied. “Unfortunately it’s going to be almost impossible to confirm this in the future,” Kipping says.

For now, it may be time to focus the search for an exomoon elsewhere. “It’s only a matter of time before we find a great one,” says Kreidberg. “I just don’t think it’s this one.”

Reference: