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Bizarre Star Could Host a Neutron Star In Its Core 73

Posted by samzenpus
from the look-at-that dept.
ananyo writes "Astronomers say that they have discovered the first example of a long-sought cosmic oddity: a bloated, dying star with a surprise in its core — an ultradense neutron star. Such entities, known as Thorne-Zytkow objects, are theoretically possible but would alter scientists' understanding of how stars can be powered. Since Thorne-Zytkow objects were first proposed in 1975, researchers have occasionally offered up candidates, but none have been confirmed."
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Bizarre Star Could Host a Neutron Star In Its Core

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  • Where is this claim? (Score:4, Interesting)

    by hubie (108345) on Wednesday January 08, 2014 @09:04PM (#45903385)

    I read TFA and I don't see where this comes from: but would alter scientists' understanding of how stars can be powered

    It sounds like Thorne and Zytkow proposed the scenario and predicted what one would observe, followed up by people like the guy quoted in the brief article (Podsiadlowski), and these astronomers are putting forth a candidate based upon their observations being similar to what the theory suggests. I'm missing the part that alters the understanding. Podsiadlowski, by the way, has been thinking about these objects for a very long time [discovermagazine.com].

  • by Anonymous Coward on Thursday January 09, 2014 @08:54AM (#45905699)

    Whether a binary system survives a supernova event is a bit complex topic, actually.

    First, the explosion is not likely to destroy the companion star, even on a fairly close orbit. Stars are really massive objects, and can readily absorb the fraction of supernova energy that happens to hit them. Second, if too much mass is ejected from the system in the explosion, the neutron star and its companion will become gravitationally unbound and drift off separately into space. Assuming a circular orbit and a perfectly symmetrical collapse of the exploding supergiant's core, this will happen if more than half of the total mass is ejected from the system. Now, there are good reasons to believe that the collapse is often slightly asymmetrical, and given the amount of energy released in the explosion, a 'slight' asymmetry might give the remaining neutron star enough 'kick' to propel it out of the host galaxy, let alone of a binary system.

    That all said, there are objects such as Cygnus X-1 that are composed of a regular star and a degenerate object that is believed to be a supernova remnant (in case of Cygnus X-1, a black hole rather than a neutron star, but the principles are the same), so it appears that at least some supernova events do not disrupt binary systems. In that case, when the companion becomes a (super)giant itself later, if it is close enough to the neutron star to fill its Roche lobe (as in Cygnus X-1) and at some point the mass transfer onto the neutron star becomes fast enough, a common envelope will form around the binary system. Common envelope causes much drag and shrinkage of the orbit; in some cases it is believed to cause both objects inside it to merge.

    Of course, much of that is rather speculative, mainly because the common envelope stage is short-lived and thus difficult to observe.

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