Astronomers May Have Just Discovered The First Planet Outside Milky Way Galaxy

Astronomers have recently found evidence of a planet candidate, which could represent the first planet outside Milky Way. They found evidence of possible exoplanet candidate in the Messier 51 Galaxy.

New Delhi: For the first time, signs of a planet orbiting a star outside the Milky Way Galaxy have been detected. Astronomers have recently found evidence of a planet candidate, which could represent the first planet outside our Milky Way Galaxy.

They found evidence of the possible exoplanet candidate in the Messier 51 Galaxy (M51), also known as the "Whirlpool" Galaxy.

This new astonishing discovery made using NASA's Chandra X-ray Observatory paves the way towards the search for exoplanets at greater distances.

The study conducted by the astronomers from the Center for Astrophysics, Harvard and Smithsonian (CfA) in Cambridge, Massachusetts, was recently published in the Nature Astronomy journal.

The system in which the evidence has been found consists of a massive star that is in orbit around a neutron star or a black hole. The temporary dimming of X-rays from this system has been detected by Chandra.

When a planet passes in front of an X-ray source around a neutron star or black hole, the X-rays dim.

This is suggestive of the fact that a planet could be present in the M51 Galaxy, according to the astronomers from the CfA.

What Are Exoplanets?

Planets outside of our Solar System are known as exoplanets. The exoplanets and exoplanet candidates found by astronomers in the Milky Way Galaxy are less than 3,000 light-years away from Earth.

An exoplanet in M51 would be 28 million light-years away from Earth, implying that it would be thousands of times farther away than the exoplanets in our galaxy.

Rosanne Di Stefano from CfA, the lead author of the study, said their team of astronomers was trying to open up a new technique of finding other worlds by searching for planet candidates at X-ray wavelengths, according to a CfA statement.

An Exoplanet Roughly The Size Of Saturn

The astronomers estimate that the exoplanet candidate in M51-ULS-1 would be roughly the size of Saturn. The discovery is enthralling, but more data is required to confirm that the candidate is an extragalactic exoplanet.

The astronomers conducted the study by observing the transits, which are events in which a star's light is blocked and a characteristic dip is produced when a planet passes in front of the star.

Di Stefano and colleagues searched for characteristic dips in the brightness of X-rays received from X-ray bright binaries — a system that is an intense source of X-rays and is composed of a normal star in close orbit with a white dwarf, neutron star, or a black hole.

X-rays could be used to detect exoplanets at much greater distances than visible light transit studies.

The team of astronomers used this strategy to detect the exoplanet candidate in a binary system known as M51-ULS-1. This binary system in the M51 Galaxy consists of a companion star with a mass 20 times that of the Sun. The star is orbited by a black hole or a neutron star. Using Chandra data, the astronomers found the X-ray transit to last three hours. During this period, the X-ray emission decreased to zero.

Nia Amara, a co-author of the study, said they would have to wait for decades to see another transit and confirm they were seeing a real planet. She added that the time required by a planet to orbit was uncertain, so they would not know when exactly to observe.