Two years ago, a group of scientists made an exciting announcement: They had discovered the first moon orbiting a planet around another star, a.k.a. the “exomoon.” Data from the Kepler Space Telescope indicated that the planet Kepler-1625b had a moon around it, and that was later backed up by observations from the Hubble telescope.
At least that’s what we thought at the time. But new research by a different group of scientists indicates that perhaps this exomoon might not exist after all.
When astronomers hunt for planets around other stars, they typically use a method called transit photometry. When an exoplanet passes in front of its star, the star gets ever-so-slightly dimmer. We can measure that dimming with telescopes like Hubble and Kepler and infer the existence of the exoplanet. This method is so successful that we’ve used it to find thousands of exoplanets.
The scientists behind the original exomoon discovery used this same method to find their moon. They found the characteristic dimming when the planet Kepler-1625b passed in front of its star, but they also noticed a secondary brightness dip shortly after the planet had passed by. That observation was confirmed with the Hubble telescope.
However, a second group of researchers has taken that same Hubble data, performed their own analysis on it, and couldn’t find the tell-tale brightness dip that indicates the presence of an exomoon. They even went over the data with the original group of researchers, and no one could figure out who was correct.
Unfortunately, it’s likely that this first exomoon discovery will always be in doubt. With such a sensitive experiment, it’s impossible to say whether the first group of researchers really did see an exomoon, or if that blip they saw in the data was just a statistical anomaly. At some point we’ll definitely find a real exomoon—probably—but until then, we’ll have to keep waiting.
Source: New Scientist
Originally published on Popular Mechanics