Astronomers Discover New Type of Bizarre, Hybrid Star Created from Red Supergiants

Astronomers have discovered a new, bizarre type of hybrid star. First proposed in 1975, this star is a hybrid of red supergiant and neutron stars that superficially resemble normal red supergiants, but differ with their distinct, chemical signatures.

The hybrid stars are called Thorn-Zytkow objects (TZOs). They're thought to be formed by the interactions of two massive stars-a red supergiant and a neutron star formed during a supernova explosion-in a close binary system. While the exact mechanism for this formation is unknown, astronomers believe that during the evolutionary interaction of the two stars, the massive red supergiant eventually swallows the neutron star, causing it to become a TZO.

The astronomers first spotted an example of the TZO by examining a spectrum of light emitted from apparent red supergiants. Yet when they analyzed the spectrum of one particular star, called HV 2112 in the Small Magellanic cloud, they found some surprising results. The star had excess rubidium, lithium and molybdenum. These elements revealed that the star was actual a TZO since the signature was unique to these types of stars.

"Studying these objects is exciting because it represents a completely new model of how stellar interiors can work," said Emily Levesque, one of the researchers, in a news release. "In these interiors we also have a new way of producing heavy elements in our universe. You've heard that everything is made of 'star stuff'-inside these stars we might now have a new way to make some of it."

The findings reveal that these stars actually exist and aren't just relegated to theory. That said, HV 2112 does display some chemical characteristics that don't quite match theoretical models.

"We could, of course, be wrong," said Philip Massey, one of the researchers, in a news release. "There are some minor inconsistencies between some of the details of what we found and what theory predicts. But the theoretical predictions are quite old, and there have been a lot of improvements in the theory since then. Hopefully our discovery will spur additional work on the theoretical side now."

The findings are published in the journal Monthly Notices of the Royal Astornomical Society Letters.