The Theoretical Ones

However, last year, the authors of a paper in Astronomy & Astrophysics found that the hypervelocity star PG 1610+062, a slowly pulsating blue star, is one bright enough to be studied in detail. Its origin, the authors say, can be traced back to the disk of our Milky Way. And it was probably ejected from our galaxy’s Carina-Sagittarius spiral arm, they write.The authors think PG 1610+062 was accelerated to such phenomenal speeds after a companion star exploded in a core-collapse supernova. Alternatively, the binary pair could have gained its velocity from gravitational interactions with young and dense stellar clusters. In such scenarios where two stars are locked in orbit around each other, their interaction with other stars in dense clusters can catapult the less massive star in the binary system into a hypervelocity trajectory. Thorne-Zytkow objects (TZOs), which exist only in theory thus far, are thought to form when a compact neutron star is surrounded by a large, diffuse envelope of hydrogen gas , say the authors of a 2014 paper in the Monthly Notices of the Royal Astronomical Society . Supergiant TZOs are predicted to be almost identical in appearance to red supergiants (RSGs), thy say. And they have unusually strong heavy-element and Lithium lines present in their spectra.First hypothesized to exist by theoretical physicists Kip Thorne and Anna Zytkow in the late 1970s, van Belle says TZOs are thought to come from a scenario wherein a star going supernova “kicks” its leftover core — now a neutron star — into another star.Van Belle cautions that this is an extremely unlikely, but not impossible, occurrence. Thus, TZOs, if they exist at all, are quite rare. Astronomers do have one candidate TZO, called HV2112, located in the Small Magellanic Cloud some 200,000 light-years away in the southern constellation of Tucana.