Using ESA’s XMM-Newton and NASA’s Chandra X-ray space telescopes, astronomers have made an important...
Using ESA's XMM-Newton and NASA's Chandra X-ray space telescopes, astronomers have made an important step in the quest to find a planet outside of the Milky Way.
Spotting a planet in another galaxy is hard, and even though astronomers know that they should exist, no planetary systems outside of the Milky Way have been confirmed so far.
Because the light from another galaxy is packed into a tiny area on the sky, it is very difficult for telescopes to distinguish one star from another, let alone a planet orbiting around them.
The usual techniques to find exoplanets in our galaxy don't work as well for planets outside of it.
"X-ray binaries may be ideal places to search for planets, because, although they are a million times brighter than our Sun, the X-rays come from a very small region. In fact, the source that we studied is smaller than Jupiter, so a transiting planet could completely block the light from the X-ray binary," explains Rosanne Di Stefano from the Center for Astrophysics, Harvard & Smithsonian in the United States, and first author of a new study published in Nature Astronomy today.
Now the game of carefully crossing off possible explanations began, before the researchers could even consider the option of an extragalactic planet.
"We did computer simulations to see whether the dip has the characteristics of a planet transiting, and we find that it fits perfectly. We are pretty confident that this is not anything else and that we have found our first planet candidate outside of the Milky Way," adds Rosanne.
That's why the team remains careful to say that they found a possible planet candidate, for which the broader community might find other explanations, although they have not been found after careful research by the team.
"The first confirmed planet outside of our Solar System was found around a pulsar, an object typically observed in X-rays. I am excited that X-rays now also play important step in the search for planets beyond the border of our galaxy," says Norbert Schartel, XMM-Newton Project Scientist for ESA. "Now that we have this new method for finding possible planet candidates in other galaxies, our hope is that by looking at all the available X-ray data in the archives, we find many more of those. In the future we might even be able to confirm their existence," says Rosanne.
Notes for editors "A possible planet candidate in an external galaxy detected through X-ray transit", by Rosanne Di Stefano et al.