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takyon [soylentnews.org] writes:

Signs of first planet found outside our galaxy [bbc.com]

Astronomers have found hints of what could be the first planet ever to be discovered outside our galaxy. Nearly 5,000 "exoplanets" - worlds orbiting stars beyond our Sun - have been found so far, but all of these have been located within the Milky Way galaxy.

The possible planet signal discovered by Nasa's Chandra X-Ray Telescope is in the Messier 51 galaxy. This is located some 28 million light-years away from the Milky Way.

[...] Dr Rosanne Di Stefano and colleagues searched for dips in the brightness of X-rays received from a type of object known as an X-ray bright binary. These objects 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 at X-ray wavelengths. 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.

The team members used this technique to detect the exoplanet candidate in a binary system called M51-ULS-1.

[...] The transit lasted about three hours, during which the X-ray emission decreased to zero. Based on this and other information, the astronomers estimate that the candidate planet would be around the size of Saturn, and orbit the neutron star or black hole at about twice the distance Saturn lies from the Sun.

Also at NASA [nasa.gov].

A possible planet candidate in an external galaxy detected through X-ray transit [harvard.edu]

Previously: Detection of Extragalactic Exoplanets and Large Organic Molecules [soylentnews.org]

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