Approximately 5,000 exoplanets have been identified outside the Solar System, but all of these worlds orbit stars in the Milky Way and are located less than 3,000 light-years away from Earth. But now astronomers have detected signs of what may be the first planet discovered in another galaxy, according to an article published this Monday in the scientific journal Nature Astronomy.
Through observations made at the Chandra X-Ray Observatory, scientists may have identified an exoplanet 28 million light-years away in the nearby galaxy Messier 51.
Astronomers believe that the possible planet — similar in size to Saturn’s — orbits the M51-ULS-1 binary system, composed of a star with a mass 20 times that of the Sun and a neutron star or black hole.
In release, NASA says that “if a planet exists in this system, it probably had a tumultuous history and a violent past”, as it had to “survive a supernova explosion that created the neutron star or black hole”.
The most used way to identify exoplanets is through the transit method, which observes the reduction of a star’s brightness whenever an exoplanet passes in front of it. However, this method is ineffective when looking for a planet so far away and outside the Milky Way.
Therefore, astronomers focused on identifying fluctuations in the X-rays emitted by the star located at M51-ULS-1, since the passage of a planet in front of a star produces drops in X-ray emissions that reach up to the land.
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