A Possible Thorne-Żytkow Object
Title: Discovery of a Thorne-Zytkow object candidate in the Small Magellanic Cloud
Authors: Emily M. Levesque, Philip Massey, Anna N. Zytkow, Nidia Morrell
In 1977, Kip Thorne and Anna Żytkow proposed that a neutron star inside of a red supergiant could exist. Such a star is known as a Thorne-Żytkow object (TŻO). This exotic object forms when the two massive stars collide.
At this point, the neutron star and the red supergiant's core begin to spiral in towards each other. Once they collide, the stars will either coalesce into a single neutron star surrounded by a gas envelope, or collapse into a black hole. A Thorne-Żytkow object would look like a normal red supergiant, but would have a different chemical signature due to the neutron star at its core.
Recently, a group of astronomers believe that they have found a candidate TŻO. HV 2112 is a star in the neighboring Small Magellanic Cloud. This star is classified as a red supergiant (M3 I) with a visual magnitude of about 13.7, a little bit dimmer than Pluto. It has a mass 15 times the mass of the Sun and a temperature of 3450 K.
What distinguishes TŻOs from red supergiants is the large amounts of unusual elements found in their spectra. It was first predicted that these elements were rubidium and molybdenum and it was later predicted to include lithium. When looking at HV 2112’s spectra, it showed abnormally large amounts of those same elements.
The abnormalities in HV 2112’s spectrum and its classification as a red supergiant agrees with the TŻO predictions, making HV 2112 a strong TŻO candidate. The authors do not rule out the possibility that HV 2112 may reside in the Milky Way, eliminating the possibility of it being a TŻO. Further studying of TŻOs will provide new models and predictions that could help identify whether HV 2112 is a real TŻO
Image: An image of HV 2112. (Credit: CDS Portal)
