Stars, galaxy and constellations

First moon outside Solar System discovered 8,000 light years away

Image credit: Pixabay

Astronomers have announced the possible discovery of the first known moon beyond our Solar System.

The moon, known as an ‘exomoon’, is reported to be a large gaseous world the size of Neptune, orbiting around a planet three times heavier than Jupiter, all of which are orbiting a nearly 10-billion-year-old Sun-like star called Kepler 1625 b, located approximately 8,000 light years from Earth.

Astronomers David Kipping and Alex Teachey, said their observations using Nasa’s Hubble Space Telescope and Kepler Space Telescope provided the first clear evidence of the exomoon, but further Hubble observations next May must be used to confirm the finding.

“We’ve tried our best to rule out other possibilities such as spacecraft anomalies, other planets in the system or stellar activity, but we’re unable to find any other single hypothesis which can explain all of the data we have,” said Kipping, from Columbia University in New York.

“The first exomoon is obviously an extraordinary claim and it requires extraordinary evidence,” Kipping said, and added the moon’s estimated size was on a scale that had “hardly been anticipated” and “defies easy explanation” based on current theories of moon formation.

It has been reported that astronomers have discovered more than 3,500 exoplanets – worlds orbiting stars other than the Sun – to date.

The researchers monitored the exoplanet known as Kepler 1625b as it passed in front of its parent star.

Lying at 8,000 light years from Earth, this 19-hour event, also named as a transit, blocked out some of the light coming from the star and Kipping and Teachey looked for two signals suggestive of an exomoon in the data from several transits.

One signal had detected a dip in the parent star’s brightness as the exomoon passed in front; the second was a delay in the planet passing in front of its star.

Following the event, Kipping said: “The location, shape and depth of this event appear consistent with a Neptune-sized moon transiting in front of the star,”

According to Kipping, about 3.5 hours after the planet’s transit ended, the Hubble telescope recorded a second smaller dimming of the star’s brightness, that indicated a moon which was described as “trailing the planet like a dog following its owner on a leash.”

The exomoon study was published in a Science Advances journal.

This September, Nasa announced its Transiting Exoplanet Survey Satellite had discovered its first two alien planets, 49 light years away.

In the same month, four stars were identified as the possible birth place of a mysterious interstellar asteroid - nicknamed ’Oumuamua - that last year invaded our Solar System. 

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