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A Team of Astrophysicists May Have Discovered the First Exoplanet Outside the Milky Way Galaxy

Published: October 27, 2021
In the Vertical Processing Facility (VPF), workers prepare the shrouded Chandra X-ray Observatory for its lift to a vertical position. (Image: NASA via Getty Images)

In a historic first, Nasa’s Chandra X-Ray Observatory has zeroed in on what is believed to be a Saturn-sized exoplanet some 28 million light-years away which, if confirmed, would mark the first time an exoplanet has been detected in a galaxy other than the Milky Way. 

Some 5,000 exoplanets — worlds orbiting stars beyond our Sun — have been catalogued since the first exoplanet was discovered in 1992; however all of these exoplanets were found right here in the Milky Way.

Most exoplanets are discovered utilizing what is called the “transit method.” When planets traverse across their host stars, or a planet transits between its star and Earth, the light coming from the host star dims, ever so slightly, allowing planet hunters the ability to gain significant knowledge about the planet by studying the light and X-rays from the host star and how they change. 

A team of astrophysicists at the Harvard-Smithsonian Center for Astrophysics led by Rosanne Di Stefano, used this method to spot the potential planet deemed M51-ULS-1b  in the Messier 51 galaxy also known as the “Whirlpool” galaxy. 

“We are trying to open up a whole new arena for finding other worlds,” Stefano said in a statement.

Needle in a haystack 

The yet to be confirmed discovery was made utilizing the European Space Agency’s XMM-Newton space telescope. Stefano’s team looked at 55 different systems in the M-51 galaxy, 64 systems in the Messier 101, or “Pinwheel galaxy,” and 199 systems in the Messier 104 galaxy, or the “Sombrero galaxy” before making the observation.

M51-ULS-1b was observed in a binary system, orbiting two large objects which are believed to be either a neutron star or a black hole which orbits a massive companion star. 

The discovery could potentially open up a whole new era of planet detection and study. 

Scientists believe it is highly unlikely that the dimming being observed could be caused by something like a cloud of interstellar dust passing between earth and the subject star.

Unfortunately, the object observed is not scheduled to pass in front of it’s star again for another 70 years, so it will be some time before scientists will be in the position to make the observation again. 

Co-author of the study, Nia Imara, a researcher at the University of California at Santa Cruz said in a statement, “Unfortunately to confirm that we’re seeing a planet we would likely have to wait decades to see another transit,” adding that, “And because of the uncertainties about how long it takes to orbit, we wouldn’t know exactly when to look.”

The team has shared the data they have collected and expect other scientists to look at the data to help confirm the discovery. 

Another co-author of the study, Julia Berndtsson, a researcher at Princeton University said, “We know we are making an exciting and bold claim so we expect that other astronomers will look at it very carefully” adding that, “We think we have a strong argument, and this process is how science works.”