A star within a star! This strange phenomenon was first proposed in 1975 by Kip Thorne and Anna Zytkow. Thorne and Zytkow were discussing what it would look like if a neutron star, a hot dense star consisting entirely of neutrons, resided in the core of a typical main sequence star; after much work they wrote a paper about these unique stars and named them Thorne-Zytkow objects (TZO).
This unique star is theorized to form when a dying red supergiant star swallows a compact, dead star. This star is only able to from a binary system containing a red supergiant and a neutron star. Red supergiant stars are colossal ranging in size from 200 to over 2,000 times larger than the sun, this extends past the orbit of saturn. A neutron star in comparison is only about 12 miles in diameter with a mass of 1.4 times that of the sun! The matter in a neutron star is so dense that on earth a teaspoon would weigh a billion tons. Like a giant cosmic pac-man, the red supergiant consumes the neutron star as it spirals into the core. Kip Thorne said the merger would create “a shell of burning material around the neutron core — a shell that would generate new elements as it burned”. The unique convection process happening in the interior of the TZO results in higher production of unusually large amounts of rubidium, strontium, yttrium, zirconium, molybdenum and lithiums. These TZO’s are some of the most luminous red supergiant stars according to Kip Thorne.
HV 2112 was discovered in the Small Magellanic Cloud that matched the predictions of a TZO given by Thorne and Zytkow in 2014. This star was found with excess rubidium, molybdenum and lithium. The Small Magellanic Cloud orbits the Milky Way and is visible to the naked eye.
What other unique, mysterious stars and other phenomenon are waiting to be discovered?