Possible Planet Found in Whirlpool Galaxy (M51)

Using the change in brightness of an X-ray binary found in observations from two X-ray telescopes, scientists may have found an extragalactic planet.

Beth Johnson

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CREDIT: X-ray: NASA/CXC/SAO/R. DiStefano, et al.; Optical: NASA/ESA/STScI/Grendler; Illustration: NASA/CXC/M.Weiss

Scientists using the ESA’s XMM-Newton and NASA’s Chandra X-ray telescopes may have found a planet in another galaxy. Not surprisingly, the methods that work for finding exoplanets here in the Milky Way, like transits and gravitational shifts, don’t work when looking at another galaxy because the visible light is hard to break apart into objects. But X-rays work really well since there are far fewer objects that shine in X-ray light, so the data collected can be analyzed to differentiate between a variety of X-ray sources.

In this case, scientists looked for X-ray binaries, which are pairs of objects such as a neutron star or black hole and a so-called donor star whose material is being pulled in by the denser object. The acceleration of the infalling star stuff produces bright X-rays, and as lead author Rosanne Di Stefano explains: 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

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Beth Johnson

Planetary scientist, podcast host. Communication specialist for SETI Institute and Planetary Science Institute. Buy me a coffee: https://ko-fi.com/planetarypan