Published: Sun, October 07, 2018
Sci-tech | By Carrie Guzman

NASA finds signs of "exomoon" in distant solar system

NASA finds signs of

The so-called exomoon, which is estimated to be the size of Neptune, was found in orbit around a very big gas planet 8,000 light-years from Earth.

Scientists have reported the first ever discovery of a moon orbiting around an "exoplanet" - a planet that exists outside of the Earth's solar system.

Astronomers can confirm those objects outside the solar system by observing a dip in the amount of light emanating from stars when they cross in front of the stars.

"This would be the first case of detecting a moon outside our solar system", said David Kipping, Assistant Professor at the Columbia University in NY.

The team of astronomers in this study consists of Alex Teachey and David M. Kipping (Columbia University, New York, USA).

Kipping has spent a decade working on the "exomoon hunt".

"If this were confirmed, then it would be a first-of-its-kind discovery, and it's important to remember that a first-of-its kind discovery demands a much higher degree of rigor, skepticism and confidence than a run-of-the-mill detection", he said.

"A companion moon is the simplest and most natural explanation for the second dip in the light curve and the orbit-timing deviation", Teachey, who is the lead author on the study published in Science Advancesthis week, said in a Columbia University release.

"It's the unknown unknowns which are ultimately uncharacterizable", Kipping said.

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The candidate moon, with the designation Kepler-1625b-i, is unusual because of its large size; it is comparable in diameter to the planet Neptune. In the case of the Earth-Moon system, an early collision with a larger body is hypothesised to have blasted off material that later coalesced into a moon.

This "exomoon" is not like any in our cosmic neighbourhood: it's the size of Neptune and orbits a planet the size of Jupiter - but with 10 times the mass.

The researchers also estimate that the new find is only 1.5 per cent of the mass of its parent planet, and the planet is several times the mass of Jupiter. Another place to look is the many gas giants identified during the Kepler mission.

Even though gas giants aren't typically considered hospitable to life, it's hard to resist comparing the pair to exoplanets and exomoons in the movies, such as Polyphemus and Pandora in "Avatar".

Kepler-1625b is an exoplanet that orbits Kepler-1625, a Sun-like star, about 8,000 light years away. Their work shows the most promising host planets would have distant orbits and long years, perhaps because gravitational interactions closer to stars can strip away moons. The transiting data associated with Kepler 1625b revealed some anomalies. More observations were needed before they could draw any conclusions, but the evidence scored them 40 hours of observation time with the Hubble telescope.

The observations measured the momentary dimming of starlight as a planet passed in front of its star, called a transit.

Kepler-1625b-i is about 1.5 percent of the mass of the planet, similar to the mass-ratio of Earth and the Moon. The planet and moon are therefore likely to be in the "habitable zone" of the star, with equilibrium temperatures likely reaching 300-350 Kelvin (27-227°C).

Although the object itself can not be seen, there are hints it exists, according to the researchers: The planet moves around its star in a way that indicates something else is pulling on it gravitationally, probably a moon. "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". But because both bodies are gaseous (which means neither are habitable as we understand it, in case you were wondering), and because of the moon's size, that raises questions about how it got there.

"If we want to do moon hunting in the future, we will have to look at planets further [than one astronomical unit, or the distance between the sun and Earth]", Teachey said. In addition, the ideal candidate planets hosting moons are in large orbits, with long and infrequent transit times.

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