Published: Thu, October 04, 2018
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Astronomers find first moon beyond our solar system

Astronomers find first moon beyond our solar system

Writing in the journal Science Advances, the researchers noted the moon would have to be unusually large to explain the observed light curve, possibly comparable to a body the size of Neptune. But there is a chance we could detect the presence of a major feature of our Solar System elsewhere: exomoons.

But that size is why it was easier to find, the researchers said. The exoplanet is a gas giant, several times more massive than Jupiter [2].

After looking through recent data from NASA's Kepler space telescope, Alex Teachey, a graduate researcher in the department of astronomy at Columbia University, and David M. Kipping, an assistant professor in the same department, spotted evidence that an exomoon might orbit the Jupiter-sized exoplanet Kepler-1625b.

The more powerful and precise Hubble telescope detected a second and smaller decrease in starlight 3 ½ hours after the planet passed in front of the star - "like a dog following its owner on a leash", as Kipping put it. The observations also confirmed Kepler 1625b passes in front of its host star earlier than expected. So, did Kepler-1625b capture its satellite? One of the planets, Kepler 1625b, caught their attention because of "little deviations and wobbles in the light curve", said Kipping.

He says they've requested more time on Hubble to do follow-up observations next May, but they are still waiting on the results of that proposal.

Due to the unfortunate timing of the Hubble observations, their time with the telescope ended after the planet transited the star, but before the candidate exomoon could fully complete its own transit. A primary goal of the Kepler mission is to identify planets that are in the habitable zones of their stars, meaning it's neither too hot nor too cold for liquid water-and potentially life-to exist.

That second dip in light may have resulted from a moon trailing the larger planet, which is orbiting the host star. "It was a shocking moment to see that light curve. But we knew our job was to keep a level head, testing every conceivable way in which the data could be tricking us until we were left with no other explanation". "Including rocky exomoons in our search for life in space will greatly expand the places we can look". Teachey said that it's likely this possible exomoon is "in some ways the lowest hanging fruit".


The researchers believe the star system to be 10 billion years old, which means it's had time to evolve.

A hunt for exomoons - bodies that orbit these distant planets - has proceeded in parallel.

They estimate the surface temperature of both to be 176 degrees Fahrenheit.

Another potential explanation is that one or more of the signals they observed were noise from the star itself. "But we did think it was interesting enough to try to get more data on". Saturn's moons were formed from its rings. There are three primary theories about how moons form.

Likewise, Teachey is not discouraged by the fact that only one of almost 300 planets surveyed appeared to host a moon. But this method relies on the moon being large enough to block a significant amount of light, which is something that's far from guaranteed.

In the meantime, a new release of Kepler data smoothed away many of those bumps, weakening the original case for a moon search.

Impact isn't possible here because these are both gaseous objects. If confirmed, it would be the first discovery of an "exomoon" in another solar system. The researchers' investigations showed that the HST-recorded transit of Kepler-1625b occurred almost 80 minutes earlier than expected, a pattern suggesting the presence of transit timing variations, or TTVs, which are among the first proposed methods to confirm the presence of exomoons. But for now, the researchers welcome comment and criticism of their hypothesis from other astronomers as part of the scientific process. He has led the field over this time, so I am delighted that his persistence has paid off. "We should expect to see something like this before we see the really small moons".

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