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Sunday, July 22, 2018

A Star Within a Star (Thorne-Żytkow Object)

In 1977, Kip Thorne and Anna Żytkow figured out what happens when a neutron star - a ball of neutronium 25 kilometers across - hits a normal star. It's called a "Thorne-Żytkow object" or TŻO. Now astronomers may have found one in the Small Magellanic Cloud!
A Thorne-Żytkow Object Is a Star Within a Star
The neutron star slowly eats its host from within. Gas gets sucked into the neutron star and gets very hot: over a billion Celsius! The heat comes from two things: energy released when infalling gas hits the neutron star, and nuclear fusion after the gas hits.
How can you tell if a star is a Thorne-Żytkow object? If it's a red giant, the neutron star will make its core a lot hotter than usual. So, the "rapid proton process" should create elements that you don't usually see in such a star.
And now astronomers have found a red supergiant with a lot more rubidium, strontium, yttrium, zirconium, molybdenum and lithium than usual
"Discovery of a Thorne-Zytkow object candidate in the Small Magellanic Cloud": https://arxiv.org/abs/1406.0001

Expanding red giant stars will swallow too-close planets. In the solar system, the sun will engulf Mercury and Venus, and may devour Earth, as well.

Credit: James Gitlin/STScI AVL

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