Astronomers catch signal from ‘Exomoon’

Astronomers catch signal from ‘exomoon’

Using the powerful Kepler Space Telescope, a team of NASA astronomers has discovered the first known moon beyond our solar system. The astronomers estimated that the “exomoon” is probably equivalent to Neptune in size and mass, and its host planet equivalent to Jupiter in size but with ten times the mass.

The astronomers couldn’t find any predictions of a Neptune-sized moon in the literature, but Dr. David Kipping, assistant professor of astronomy at Columbia University in New York, noted that nothing prevents one in physics.

Dr. Kipping said in a statement, “I’d say it's the best [candidate] we've had. Almost every time we hit a candidate, and it passes our tests, we invent more tests until it finally dies ... in this case we've applied everything we've ever done and it's passed all of those tests.”

To date, more than three thousand exoplanets have been discovered. A hunt for exomoons has been proceeding in parallel. But these extrasolar satellites have thus far been lingering at the limits of detection with existing techniques.

A research paper about the candidate exomoon appeared recently on the Arxiv pre-print site. Astronomers are now preparing to carry out follow-up observations with the help of Hubble space telescope in October.

The research paper added...

Exoplanets are found by noting the dimming of stars that occurs as a planet passes between Earth and the star. A moon would be found in roughly the same way, the researchers note, by looking for dimming that occurs in the light reflected from a planet caused by the transit of a moon. Kipping and his team report that they recorded three such dippings as the planet made three trips around its star. They have given their find a statistical confidence of slightly above 4 sigma, noting that the dipping they observed could be chalked up to a fluke in the data—there also exists the possibility that the dimming has another cause. They note that the star system is approximately 4000 light years away, which means the light from the planet is extremely dim to begin with.

An exomoon is a moon orbiting an exoplanet. Many moons have been found in our solar system and many planets outside of it, but to date, no one has captured evidence of a moon orbiting one of those exoplanets. This might change, as the team studying data from the Kepler Space Telescope believe they have found strong evidence for a moon orbiting a planet which is itself orbiting a star called Kepler-1625.

The team expects their finding to be verified (or quashed) by data from the Hubble Space Telescope, which offers much better data, sometime in the near future. But while they wait, they are already developing theories about the exomoon—if it truly exists, it would have to be much larger than our moon in order to detect it, perhaps as large as Neptune. That would mean the planet it is orbiting wis also quite large, likely as large as Jupiter. If that is the case, its size suggests that it would likely have formed later than moons in our solar system. It would also make the first observed exomoon the largest moon ever observed.