Are there planets in other galaxies? It has been a recurring question in the field of astronomy since, although we have discovered thousands of planets in our galaxy beyond the solar system, there had been no identification in other galaxies. Although there is no reason to think that other galaxies do not host planets as well.
All the exoplanets that have been discovered so far (more than 4,800) have been detected in the Milky Way, most within 3,000 light years of Earth. If this planet is confirmed, it would be “thousands of times farther away than those of the Milky Way,” NASA said in a statement.
The first known planet in another galaxy?
Scientists used NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM-Newton telescope to find what appears to be the first extragalactic planet, located in the spiral galaxy Messier 51 (M51), also known as the galaxy. of the Whirlpool.
The team reports in their study published in the journal Nature Astronomy, of a drop in the luminosity of a bright X-ray source (XRB) known as M51-ULS-1 . The source is likely to be a neutron star or a black hole orbited by a massive star located in the Whirlpool galaxy (M51). According to the researchers, both objects are orbited by the potential planet. As it moves around the two objects, it ends up overshadowing the X-ray source, producing a drop in luminosity.
“We always assume that there would be planets in other galaxies, but actually finding something is a beautiful thing. It is a pure humbling experience,” explains astrophysicist Rosanne Di Stefano of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts and leader of the work.
This potential world, M51-ULS-1b, therefore orbits both a massive star and a dead star in the Whirlpool galaxy, some 28 million light-years from Earth. To identify it, the researchers analyzed a total of 2,624 possible transits in three galaxies: M51 (the Whirlpool galaxy), M101 (the Pinwheel galaxy) and M104 (the Sombrero galaxy).
Only one showed a clear signal similar to a planet. On September 20, 2012, an object had blocked all X-rays from the X-ray binary M51-ULS-1 for approximately three hours.
After ruling out gas clouds, fluctuations in the X-ray source itself, or other explanations for the drop in luminosity, experts concluded that the object is likely a Saturn-sized planet orbiting hundreds of times the distance between Earth and Earth. the Sun (tens of astronomical units).
How to confirm it?
The way to confirm this discovery would be to identify more X-ray eclipses , both inside and outside the Milky Way. But, having made one detection, making another seems only a matter of time; yes, any confirmation could take many decades , taking into account that the possible planet is orbiting at approximately the same distance as Saturn to our Sun.
Referencia: Rosanne Di Stefano, A possible planet candidate in an external galaxy detected through X-ray transit, Nature Astronomy (2021). DOI: 10.1038/s41550-021-01495-w. www.nature.com/articles/s41550-021-01495-w
