Saturday, July 29, 2017

Possible First Exomoon Detected

Artist's rendering of what an exomoon (blue) orbiting an exoplanet might look like. Credit: NASA Wikimedia

A signal has been spotted that might be the first moon detected outside our solar system, and researchers are gearing up to use the Hubble Space Telescope to confirm it. David Kipping at Columbia University in New York and his colleagues have been using the Kepler Space Telescope to search for moons around other worlds for years, but they haven’t found any yet. “We’ve had candidates in the past and investigated them, and most of them have evaporated,” said Kipping.

The candidate moon is known as Kepler-1625 b I and is observed around a star that lies some 4,000 light-years from Earth. On account of its large size, team members have dubbed it a "Nept-moon".

Kepler-1625 b is a candidate planet that Kepler, NASA’s flagship exoplanet mission, had previously observed. Periodic dips in the host star’s brightness indicated that a massive object was crossing the line of sight from the star to Earth; but the dips were lopsided, suggesting that perhaps instead of one object there were two: a Jupiter-sized planet with a Neptune-sized moon in tow. If this were indeed an ‘exomoon’, it would have been a long-awaited discovery. But it was still a big if.

“It wasn’t something we were planning on announcing, because at this point it’s only a candidate,” said Kipping, who would have preferred to be more cautious with the news. “It really only takes the slightest misstep in our language to miscommunicate the reality of what we have.”

If Kipping and his team are able to verify this detection, as well as being the first exomoon we’ve ever seen, it would be a much larger moon than we’ve ever seen before. This indicates that there may be even more types of moon than the many we’ve already observed.

“It would be analogous to the first exoplanet detections, which defied our prejudices from the solar system as well,” says Duncan Forgan at the University of St Andrews in the UK.

A paper about the candidate moon is published on the arXiv pre-print site.

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