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Astronomers Find Star-Within-a-Star, 40 Years After First Theorized
derekmead writes: After 40 years, astronomers have likely found a rather strange celestial body known as a Thorne–Zytkow object (TZO), in which a neutron star is absorbed by a red supergiant. Originally predicted in the 1970s, the first non-theoretical TZO was found earlier this year, based on calculations presented in a paper forthcoming in MNRAS.
TZOs were predicted by astronomer Kip Thorne and Anna Zytkow, who wasthen postdoctoral fellow at CalTech. The pair imagined what might happen if a neutron star in a binary system merged with its partner red supergiant. This wouldn't be like two average stars merging. Neutron stars are the ancient remnants of stars that grew too big and exploded. Their cores remain small — about 12.5 miles across — as they shed material out into space. Red supergiants are the largest stars in the galaxy, with radii up to 800 times that of our sun, but they aren't dense.
TZOs were predicted by astronomer Kip Thorne and Anna Zytkow, who wasthen postdoctoral fellow at CalTech. The pair imagined what might happen if a neutron star in a binary system merged with its partner red supergiant. This wouldn't be like two average stars merging. Neutron stars are the ancient remnants of stars that grew too big and exploded. Their cores remain small — about 12.5 miles across — as they shed material out into space. Red supergiants are the largest stars in the galaxy, with radii up to 800 times that of our sun, but they aren't dense.
- Is the research reliable?
Well, the Monthly Notices of the Royal Astronomy Society is one of the longest running astronomy journals in the world, and, to my knowledge, has never done anything substantial to impugn its reputation. It also has a comparatively large impact factor. All signs that the peer review is considered of good quality.
- How can such a thing be stable? Is there any particular process that keeps one star inside the other?
Why wouldn't it be stable? More gravity means more fusion, not less.
The theory says it's a companion star that goes nova, and then is gradually de-orbitted into the larger gas giant.
- What even /is/ such a body? If you were to travel from the outside to the midpoint of the body, would you encounter two barriers of destructing heat, with some emptiness (I'd like to say "vacuum" but of course space is not exactly a vacuum) in between?
Or is it actually just something entirely unlike what you would imagine when someone says "star within a star"?
Oh, and just now I realize you hadn't read the summary. It's a neutron star inside a star. A neutron star is essentially a block of neutronium(essentially a gigantic neutron only nucleus) with some attached hanger on high energy plasma around.
It lasts for several hundred thousand years but the red giant is eventually absorbed into the neutron star which becomes a slightly larger neutron star or possibly a black hole.
So the red giant is just a big meal that takes a while to eat. But if you look around enough, you can find one in the middle of its course.
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Yeah I clicked through to the article. No idea why I did that but:
It's red supergiant with too much lithium, molybdenum and other metals. There's 'something' in there.
Gravity keeps one star inside the other, as in, the neutron star fell into the supergiant. It sank to the center.
Around the surface of the neutron star is now where the 'core' of the red supergiant is, still burning hydrogen (or was it helium?) as a red supergiant should.
Sounded like some subtle measurements to distinguish this one from all the other red supergiants they looked at.
I should get karma for this. Just sayin'.
Hmm ... interesting to think about. A red giant is much bigger than our sun, yes, but its mass is typically similar. Think of it as red-hot vacuum, except for the core. But as the neutron star fell into it, it would draw out a visible tendril of material - and when that tendril touched the neutron star, *then* you'd see fireworks. Gravitational accretion is more efficient than fusion at releasing energy: you'd see a point of bright blue light (peaking in x-rays) at the neutron star, with the pressure of the emitted light probably blowing a cavity into the side of the red giant.
Until the neutron star fell deeply into the red giant, the top of the cavity closed over, and you had just a red giant with a little surprise inside. From the abstract of the paper, the only way they could even identify this object as a special red giant is the presence of certain chemicals in its upper layers, probably produced in the hot-burning region around an included neutron star.
(Astrophysicist here, but not the right kind to be an expert on this.)