The idea of a star-within-a-star is weird. Known as a Thorne-Żytkow Object, a nesting-doll star was first proposed by two physicists, Kip Thorne and Anna Żytkow, back in the '70s. But no one has ever seen one. Now, though, Alexandra Witze reports at Nature, astronomers have found the best candidate yet. Although a neutron star is only ten miles or so across, its gravitational pull is so strong that it could draw matter away from its huge but more diffuse companion. In the process, it would slow down, like a ship dragging an anchor. Eventually the neutron star, in an ever-shrinking orbit, would plow into the outer layers of its neighbor. After a few thousand years it would spiral down into the star’s center, demolishing the existing stellar core but leaving the rest of the star essentially intact. A red giant that has been violated in this way has come to be called a Thorne-Zytkow object--even though no one has ever seen one.
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