Published: Sat, October 06, 2018
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Hubble finds compelling evidence for a moon outside the solar system

Hubble finds compelling evidence for a moon outside the solar system

Evidence of this exomoon was observed through a dimming of light from the exoplanet Kepler-1625b about 7,800 light years from earth. They noticed that after Kepler-1625B crossed in front of its star there was another decrease in measurable brightness 3.5 hours late. These enabled astronomers to derive the masses of the planets directly from the transit light curve. Second, three-and-a-half hours after the transit, a much smaller second transit occurred, which involved a very slight dimming of the star's light.

In Star Wars VI we first meet the Ewoks living on the Forest Moon of Endor.

In addition, as a planet and its moon orbit a common centre of gravity, it causes the planet to wobble away from its predicted location. 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. These observations ended before a full transit of the moon could be measured but the evidence provided were the most compelling yet for the first known planetary satellite around an exoplanet. Of the eight planets, only mercury and Venus they are not. That made it easier to detect secondary brightness dips that might represent an exomoon.

The researchers note the planetary wobble could be caused by the gravitational pull of a hypothetical second planet in the system, rather than a moon.

"A companion moon is the simplest and most natural explanation for the second dip in the light curve and the orbit-timing deviation".

Spotting an exomoon is done in largely the same way, and if the team's measurements are on point we're looking at an absolutely enormous moon and an even larger host planet. The planet itself is several times heavier than Jupiter, and its mass, the moon is 1.5% of the mass of the planet. The exomoon is estimated to be roughly the size of Neptune, the smallest of our solar system's four gas planets, with a diameter of about 30,600 miles (49,000 km). The exomoon's mass is about 1.5 percent that of its planet.


Kepler 1625b and its satellite, however, are gaseous, not rocky, and, therefore, such a collision may not lead to the condensation of a satellite.

Further efforts to find exomoons will likely focus on Jupiter-sized planets that orbit their stars at distances greater than the Earth orbits the Sun. They observed the system throughout a predicted transit of the planet Kepler-1625b over the course of 40 hours.

It's not like the exomoon in "Avatar" or Endor from "Star Wars", Teachey said, "but going forward, I think we're opening doors to finding worlds like that".

"This intriguing finding shows how NASA's missions work together to uncover incredible mysteries in our cosmos", said Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate at Headquarters, Washington. Their results were published Wednesday in the journal Science Advances.

"The fact is, it's so odd and it's the first of its kind", says David Kipping, an astronomer at Columbia University. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. But there's no evidence of more planets in the system.

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