Astronomers believe they have found what could be the first planet ever to be discovered outside the Milky Way galaxy.
So far, nearly 5,000 exoplanets have been found; but all of them have been located within our galaxy.
The possible planet signal discovered by NASA’s Chandra X-Ray Telescope is in the Messier 51 galaxy.
This is located some 28 million light-years away from the Milky Way galaxy.
This new finding is based on transits. These are the passage of a planet in front of a star that blocks some of the star’s light and yields a characteristic dip in brightness that can be detected by telescopes.
Experts have used this technique to find thousands of exoplanets.
Typically, these objects contain a neutron star or black hole pulling in gas from a closely orbiting companion star.
So the material near the neutron star or black hole becomes superheated and glows at X-ray wavelengths.
As the region producing bright X-rays is small, hence a planet passing in front of it could block most or all of the X-rays, which makes the transit easier to spot.
The team members used this technique to detect the exoplanet candidate in a binary system called M51-ULS-1.
The new optical and infrared telescopes would not be able to compensate for the problems of crowding and dimness; therefore, the observations at X-ray wavelengths are likely to remain the primary method for detecting planets in other galaxies.
At the same time, scientists believe that the method of microlensing might also prove to be helpful in identifying extra-galactic planets.