An Extragalactic Extrasolar Planet?

In "Extrasolar Planets Thwart Cosmic Evolution", we looked at three articles by astrophysicist Dr. Jason Lisle. He discussed the history of exoplanets, the methods used for detection, how astronomers know their composition, and more. Those planets are within our own galaxy.

Detecting them is fascinating enough, but prepare to be impressed again because there is a strong possibility that an exoplanet outside our galaxy has been found. Those fun-loving astronomers have given it the whimsical name of M51-ULS-1b. This discovery is quite interesting.

X-ray: NASA/CXC/SAO/R. DiStefano, et al.; Optical: NASA/ESA/STScI/Grendler; Illustration: NASA/CXC/M.Weiss
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This is a bigly-huge distance away, and the detection is reminiscent of that used for discovering the first exoplanets (this method may lead to further discoveries out there, thataway). In both cases, planets are around massive objects, but the latest one has quite a bit happening. It is in the Whirlpool Galaxy, and creates problems for cosmic evolution speculations. Also, people may ask if it has life. Not possible.

[R]esearchers looked around an X-ray bright binary (XRB). An XRB comprises a superdense object, either a neutron star or black hole, with a closely orbiting companion star. The two objects are close enough for the gravity of the superdense body to pull in gas from the star. The material is pulled so strongly that it releases enormous amounts of its gravitational potential energy as X-rays. . . .

Also, the X-ray emitting area is very small. A neutron star is only about 10 km in radius but about 1.4 times the mass of our sun, so is amazingly dense. A tablespoon of neutron star matter has a mass of about a billion tonnes, about the same as Mt Everest. A black hole is even smaller—in fact, a point of mass with infinite density. In either case, a planet could block 100% of the associated X-ray source. By comparison, planets have a tiny cross-sectional area compared to the parent star, so they block only a tiny percentage of the light. Actually, when the blocking object’s apparent size is larger than the blocked object’s, the precise term is not transit but occultation.

To read the rest of this really far out article, set your browser coordinates to "Planet found outside our galaxy?" We have one more article to ponder, so be sure to find your way back here.

While there is necessarily some overlap, astronomer Dr. Danny Faulkner adds some details that increase our understanding.

What kind of object is M51-ULS-1? Like many X-ray sources, M51-ULS-1 is a close binary star, with one of the component stars being a compact object. . . . As the two stars in an X-ray binary orbit one another, the strong gravity of the compact object raises tides on its companion, an ordinary star, strong enough to transfer matter from the star to the compact object. Because of conservation of angular momentum, the matter can’t fall directly onto the compact object. Instead, the matter collects onto an accretion disk around the compact object. . . . It is the very hot part of the accretion disk that emits the X-rays. The hot, X-ray–emitting region of the accretion disk is about the size of a small planet.

To read the entire article, see "M51-ULS-1b: The First Extragalactic Exoplanet."