Published: Sat, October 06, 2018
Sci-tech | By April Francis

Hubble finds compelling evidence for a moon outside the solar system

Hubble finds compelling evidence for a moon outside the solar system

In a stellar system 8000 light-years from Earth, astronomers have found the first compelling evidence for a Neptune-sized moon orbiting a Jupiter-sized planet. He and his colleague David Kipping are careful to call their discovery a "candidate moon", noting that more studies are required to confirm its existence. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University's Astronomy Online program.

In principle this anomaly could also be caused by the gravitational pull of a hypothetical second planet in the system, but the Kepler Space Telescope found no evidence for additional planets around the star during its four year mission.

The event of a planet passing in front of a star is called a transit, and Kepler-1625b's takes about 19 hours. Currently, there are just a handful of such planets in the Kepler database.

The detection of the candidate exomoon - moons orbiting planets in other star systems - is unusual because of its large size, comparable to the diameter of Neptune. Yet there were weird signatures in the flicker of this far-flung star system. Both the timing effects and the dimming of the star that we see in the data correspond with the mood model description so the astronomers allocated 40 hours of observation time on the Hubble telescope. As detailed in the researchers' publication, the Hubble telescope picked up a smaller dimming about 3.5 hours after the first one, suggesting a second body following the first one. And finding future moons will require looking at planets much further out from their stars, something that is hard now, but should possible once the powerful but long-delayed James Webb Space Telescope finally begins scanning the skies.

While thousands of exoplanets have been identified over the time, astronomers couldn't detect a moon outside our solar system.

Prof Kipping said. "We can expect to see really tiny moons". Kipping and Teachey weren't even sure how such a moon might have formed. Any larger, and this planet would technically be a brown dwarf. They estimate it to be 1.5 percent the mass of its planet and the mass ratio between planet and moon to be close to that of the Earth-Moon system.

The moon is estimated to be only 1.5 per cent the mass of its companion planet, which itself estimated to be several times the mass of Jupiter.

"It's raising new questions about sort of the dynamical processes that go on to create the planets and moons", Teachey said. Teachey noted that astronomy is biased toward finding bigger things - they're easier to spot. If confirmed, this discovery will change everything we know about moons, and I, for one, am beyond excited.

This is also not the first time that Kepler-1625b-i has been observed. A moon could be the culprit for such a distortion in the trajectory of a planet.

Although further observations by Hubble are needed to fully confirm the existence of Kepler-1625b-i, as such gargantuan moons are unknown in our own Solar System, if it turns out to be real then it may yield new insights into the development of planetary systems and may cause astronomers to revisit theories of how moons form, said Teachey. "But we did think it was interesting enough to try to get more data on".

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