Researchers say a new planet has been discovered outside the Milky Way

Astronomers have discovered tempting signs of a planet in a star system outside the Milky Way, which if confirmed would be the first to be found in any other galaxy.

Discovery, reported in a study published on Monday. In the journal Nature Astronomy, he shows a new technique for finding distant worlds and could significantly expand the search for so-called exoplanets.

“It’s always fun to find something that’s first of its kind,” said the study’s lead author, Roseanne Di Stefano, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics. “When we started finding planets locally, it made sense to have planets in other galaxies, but that’s really humbling and exciting.”

The possible planet has been discovered in a spiral galaxy called Messier 51, also known as the Whirlpool Galaxy, which is more than 23 million light-years from Earth.

The first exoplanets, or planets outside the solar system, were discovered in the 1990s and required a range of sophisticated detection techniques. Since then, however, NASA missions such as the Kepler space telescope and the Transiting Exoplanet Reconnaissance satellite have discovered an abundance of worlds across the galaxy.

more than 4000 outer planets They have been discovered and confirmed, but so far they have all been in Milky Way. Most of them were also less than 3,000 light-years away from Earth. If confirmed, the planet in the Whirlpool Galaxy would be a thousand times more distant than any other identified alien planet.

The potential extraterrestrial world is found in an X-ray binary system, a type of star system that creates and emits X-rays and is usually made up of an ordinary star and a collapsing star, such as a neutron star or black hole.

Astronomers often use what is known as the “transit method” to search for planets. Transits occur when a planet orbits in front of its parent star, temporarily blocking part of it and causing a noticeable interruption in the star’s light. Di Stefano and colleagues applied the same basic idea, but instead of using optical light, they monitored changes in the X-ray brightness of the Whirlpool galaxy’s binary star system.

The area that produces bright X-rays is relatively small, Di Stefano said, allowing him to see transits that block most or all of the X-ray emissions.

“It’s a very clear sign,” she said.

Using data from NASA’s Chandra X-ray Observatory, Di Stefano and colleagues observed that the crossing took about three hours, and they were able to estimate the size of the object that completely obscured the X-ray source. They estimate that the potential planet is the size of Saturn and that it is much farther from its star than Earth is from the Sun.

Bruce MacIntosh, a professor of physics at Stanford University, who was not involved in the research, said the discovery is exciting because, if confirmed, it would show not only that planets are distributed throughout the universe, but also in unlikely places.

“The good thing is that they found a planet orbiting a neutron star that is part of a system that has gone through a supernova explosion and has an interesting and complex evolutionary history,” he said. “It’s exciting that a planet can survive when its star explodes.”

It will likely take some time to confirm the existence of a planet in the X-ray binary. The planet’s distant orbit means it will likely be around 70 years before astronomers can see another transit.

“Because of the uncertainty about how long the orbit lasts, we don’t know exactly when to look,” says study co-author Nia Imara, associate professor at the University of California, Santa Cruz. He said in a statement.

Macintosh said the X-ray transit screening method is “smart” but is unlikely to be used to find hundreds of thousands of planetarium candidates, because it also depends on luck.

“You can only see the crossing if there are things between you and the thing you are looking at,” he said. “And you only see it pass the target body for a few minutes or hours.”

However, according to Di Stefano, it is gratifying that the new method of searching for exoplanets outside the galaxy, which she and her colleagues first looked at in 2018, has led to such a tempting result.

“We didn’t know if we were going to find something and we were very lucky that we did,” she said. “Now we expect other groups around the world to study more data and make more discoveries.”