Astronomers discover first Thorne-Zytkow object, a bizarre type of hybrid star

night sky
Credit: A. Fujii

In a discovery decades in the making, scientists have detected the first of a "theoretical" class of stars first proposed in 1975 by physicist Kip Thorne and astronomer Anna Żytkow. Thorne-Żytkow objects (TŻOs) are hybrids of red supergiant and neutron stars that superficially resemble normal red supergiants, such as Betelguese in the constellation Orion. They differ, however, in their distinct chemical signatures that result from unique activity in their stellar interiors.

TŻOs are thought to be formed by the interaction 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 is uncertain, the most commonly held theory suggests that, during the evolutionary interaction of the two stars, the much more massive red supergiant essentially swallows the neutron star, which spirals into the core of the .

While normal red supergiants derive their energy from nuclear fusion in their cores, TŻOs are powered by the unusual activity of the absorbed in their cores. The discovery of this TŻO thus provides evidence of a model of stellar interiors previously undetected by astronomers.

Project leader Emily Levesque of the University of Colorado Boulder, who earlier this year was awarded the American Astronomical Society's Annie Jump Cannon Award, said, "Studying these objects is exciting because it represents a completely new model of how can work. 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 study, accepted for publication in the Monthly Notices of the Royal Astronomical Society Letters, is co-authored by Philip Massey, of Lowell Observatory in Flagstaff, Arizona; Anna Żytkow of the University of Cambridge in the U.K.; and Nidia Morrell of the Carnegie Observatories in La Serena, Chile.

The astronomers made their discovery with the 6.5-meter Magellan Clay telescope on Las Campanas, in Chile. They examined the spectrum of light emitted from apparent red supergiants, which tells them what elements are present. When the spectrum of one particular star—HV 2112 in the Small Magellanic Cloud―was first displayed, the observers were quite surprised by some of the unusual features. Morrell explained, "I don't know what this is, but I know that I like it!"

When Levesque and her colleagues took a close look at the subtle lines in the spectrum they found that it contained excess rubidium, lithium and molybdenum. Past research has shown that normal stellar processes can create each of these elements. But high abundances of all three of these at the temperatures typical of red supergiants is a unique signature of TŻOs.

"I am extremely happy that observational confirmation of our theoretical prediction has started to emerge," Żytkow said. "Since Kip Thorne and I proposed our models of stars with neutron cores, people were not able to disprove our work. If theory is sound, experimental confirmation shows up sooner or later. So it was a matter of identification of a promising group of , getting telescope time and proceeding with the project."

The team is careful to point out that HV 2112 displays some chemical characteristics that don't quite match theoretical models. Massey points out, "We could, of course, be wrong. 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."

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New discovery could be a Thorne-Zytkow object

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Citation: Astronomers discover first Thorne-Zytkow object, a bizarre type of hybrid star (2014, June 4) retrieved 21 September 2019 from
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Jun 04, 2014
I recall reading about some Hawaii professor who showed that if a star absorbed a neutron star, the star explodes . . .

. . . of course, this is a supergiant star, not some average star like the Sun; maybe the supergiant has enough weight to hold together.

Jun 04, 2014
What happens when a supergiant explodes, pushing a good portion of its mass onto the surface of a neutron star inside it? Another explosion? GRB?

Jun 04, 2014
So the neutron star eventually becomes an even bigger neutron star, and then collapses into a black hole?

Jun 04, 2014
Wow....anyone else here remember a member that had his own theoey about how neutron stars were powering stars. He always signed his posts with "formally worked for NASA". I can recall his name. We aĺl said he was nuts. Who would have thought, huh? :D

Jun 04, 2014

Ah, yeah, good ol' O.M., and his insistence that our sun is one of these objects. Unfortunately for him, his predictions doesn't match observations, and these researchers have pointed out why this is so, for Sol, at least, in that emission spectra of our star don't in any way resemble those expected from a TZO.

So, it appears that the best that can be said of him is that he was correct in general terms while being incorrect in the particular.

Jun 04, 2014
Oliver something or other....

Jun 04, 2014
This comment has been removed by a moderator.

Jun 04, 2014
Oliver Manuel (as if you don't remember). His conjecture involved Neutron Repulsion and he had some evidence in support. These observations DO tend to support some of his arguments.

Jun 04, 2014
Just to avoid being shot as a messenger, my comment does not imply that I have an opinion on Neutron Repulsion as a force to be reckoned with. I don't believe that Neutrons as an entity in or of themselves exist. Well, not on Thursdays anyway.

Jun 05, 2014
This comment has been removed by a moderator.

Jun 05, 2014
Who is the "iron sun" wacko? Probably not the man you mention, but it triggered the memory..

The very same wacko. Oliver Manuel. See here:
If you dare.

For even more disturbing info see here: http://journalist...ple.html

Jun 05, 2014
The online wackos and trolls are often weird psychopats IRL too.
The story about Oliver is simply disgusting.

There are more strange creatures on this site, especially related to articles mentioning climate or religion.

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