Posted on Jul 28, 2017 in Uncategorized
A team of astronomers has potentially discovered a signal detected by Nasa's Kepler Space Telescope from Kepler moon-1625b I orbiting around a a G-type star that lies some 4,000 light-years from Earth. This is the first known moon beyond the Solar System that appears to be about the size and mass of Neptune that circles Kepler planet Kepler-1625, a gas giant exoplanet that takes 287.38 days to complete one orbit of its star. To date, these extrasolar satellites have lingered at the limits of detection with current techniques.
The discovery of alien moons opens up an exciting new frontier in the continuing hunt for habitable worlds outside the Solar System. With the confirmation of exomoons likely right around the corner, researchers have begun addressing the unique and un-Earthly factors that might affect their habitability.
Dr David Kipping, assistant professor of astronomy at Columbia University in New York, who has spent "most of his adult life" looking for exomoons, says "We would merely describe it at this point as something consistent with a moon, but, who knows, it could be something else."
The promising signal was observed during three transits – fewer than the astronomers would like to have in order to confidently announce a discovery. The researchers will conduct follow-up observations with Hubble in October
Kipping amd his Columbia colleague Alex Teachey and citizen scientist Allan R Schmitt, assigns a confidence level of four sigma to the signal from the distant planetary system. The confidence level describes how unlikely it is that an experimental result is simply down to chance. If you express it in terms of tossing a coin, it's equivalent to tossing 15 heads in row.
"We're excited about it… statistically, formally, it's a very high probability," Kipling told the BBC. "But do we really trust the statistics? That's something unquantifiable. Until we get the measurements from Hubble, it may as well be 50-50 in my mind." Astronomers now plan to carry out follow-up observations with Hubble in October.
A current theory of planetary formation suggests such an object was captured by the gravity of the planet later on in the evolution of this planetary system.
Astronomers have their fingers crossed that within the haul of data collected by NASA's Kepler mission, which has already detected nearly three thousand possible exoplanets, hide the signatures of the very first exomoons. "The first exomoons that we find will be large – maybe Mars- or even Earth-sized – and therefore intrinsically more likely to be habitable than small moons," says René Heller, a postdoctoral research associate at the Leibniz Institute for Astrophysics in Potsdam, Germany. "With Kepler finding many more giant planets than terrestrial planets in stellar habitable zones, it's really important that we try to figure out what conditions might be like on the moons of these giants to gauge if they can host extraterrestrial life."
In a series of papers, Heller and his colleague tackled some of the big-picture problems to habitability posed by Rory Barnes from the University of Washington and the NASA Astrobiology Institute by the relationship between exomoons and their host planets.
Heller and Barnes have proposed a circumplanetary "habitable edge," similar to the well-established circumstellar "habitable zone." This zone is the temperature band around a star within which water neither boils off or freezes away on a planet's surface – not too hot, not too cold, thus earning it the nickname "the Goldilocks zone."
The Daily Galaxy via BBC News and NASA
Image credit: Science Photo Library