In a first, NASA finds evidence of possible planet outside of Milky Way galaxy

The possible planet candidate is located in the spiral galaxy Messier 51 (M51), researchers estimates the exoplanet candidate would be roughly the size of Saturn.

New Delhi: The US space agency reported that for the first time it has spotted signs of a planet transiting a star outside of our Milky Way galaxy. NASA`s Chandra X-ray Observatory made the discovery thus opening up a new avenue to search for exoplanets at greater distances than considered earlier.

NASA in a statement said that the possible planet candidate is located in the spiral galaxy Messier 51 (M51), also called the Whirlpool Galaxy because of its distinctive profile. 

"We are trying to open up a whole new arena for finding other worlds by searching for planet candidates at X-ray wavelengths, a strategy that makes it possible to discover them in other galaxies," said Rosanne Di Stefano of the Center for Astrophysics at Harvard and Smithsonian (CfA) in Cambridge, Massachusetts, who led the study.

The exoplanet candidate was spotted in a binary system called M51-ULS-1. This system contains a black hole orbiting a companion star with a mass about 20 times that of the Sun. The team estimates the exoplanet candidate would be roughly the size of Saturn, and orbit the neutron star or black hole at about twice the distance of Saturn from the Sun.

Researchers would need more data to verify the interpretation as an extragalactic exoplanet. Since the planet candidate`s orbit is massive it means that the next time it crosses in front of its binary partner again not for about 70 years, in the process thwarting any attempts at confirming the observation for decades, NASA said.

Up until now all other known exoplanets and exoplanet candidates in the Milky Way galaxy has been found and almost all of them were placed less than about 3,000 light years from Earth. The exoplanet in M51 would be about 28 million light years away, NASA said.

The findings are published in the journal Nature Astronomy..