Historic: NASA Says First Possible Planet Outside Milky Way Detected

For the very first time, humankind has witnessed signs of a possible planet transiting a star outside of our Milky Way galaxy.

NASA reported on Monday that utilizing their Chandra X-ray Observatory, they discovered the possible planet in the spiral galaxy Messier 51 (M51), aka the Whirlpool Galaxy.

All prior exoplanets (planets outside our Solar System) have been found within the Milky Way galaxy. But this new candidate lies roughly 28 million light-years away, “meaning it would be thousands of times farther away than those in the Milky Way,” NASA explained.

Harvard astrophysicist Rosanne Di Stefano, who led the study that was published in Nature Astronomy, stated, “We are trying to open up a whole new arena for finding other worlds by searching for planet candidates at X-ray wavelengths, a strategy that makes it possible to discover them in other galaxies.”

Instead of using the traditional method of using both ground-based and space-based telescopes to look for dips in optical light, which can be triggered by a planet in front of a star blocking some of the star’s light. The method used for the study involved looking for dips “in the brightness of X-rays received from X-ray bright binaries,” NASA reported, adding:

These luminous systems typically contain a neutron star or black hole pulling in gas from a closely orbiting companion star. The material near the neutron star or black hole becomes superheated and glows in X-rays. Because the region producing bright X-rays is small, a planet passing in front of it could block most or all of the X-rays, making the transit easier to spot because the X-rays can completely disappear. This could allow exoplanets to be detected at much greater distances than current optical light transit studies, which must be able to detect tiny decreases in light because the planet only blocks a tiny fraction of the star.

The new planet candidate exists in a binary system, which “contains a black hole or neutron star orbiting a companion star with a mass about 20 times that of the Sun. The X-ray transit they found using Chandra data lasted about three hours, during which the X-ray emission decreased to zero. Based on this and other information, the researchers estimate the exoplanet candidate in M51-ULS-1 would be roughly the size of Saturn, and orbit the neutron star or black hole at about twice the distance of Saturn from the Sun.”

NASA said that, because of the huge