What are Thorne-Żytkow objects?
To the untrained eye, Thorne-Żytkow objects, or TŻOs, are unassuming red supergiants. Except they harbour a dark secret inside: instead of an elementforging furnace in their cores, there lies a stellar corpse called a neutron star. In other terms, a TŻO is nothing more than a dead star masquerading as a living one.
There are many ways nature can create this strange combination. Some astronomers speculate a red supergiant could capture a neutron star travelling close by. Others posit that a single star’s innermost layers could collapse in on themselves, form a neutron star, but maintain a red supergiant appearance on the outside. So far these stars are theoretical; we’ve found a few candidates proving they exist – the most famous, HV 2112, is located 60 kiloparsecs from Earth. Astronomers find proof by using spectroscopy. A TŻO would have an odd mixture of elements melded on the hot, dense surface of the inner neutron star that would not exist in a true red supergiant. Moreover, we can also use gravitational waves to make observations. If we search for gravitational waves from a suspected TŻO, we would ‘see’ straight through its red supergiant mask and reveal the neutron
star underneath!
“instead of an elementforging furnace in their cores, there lies a stellar corpse called a neutron star”
Lindsay DeMarchi