Saturday, July 10, 2021

A star within a star(THORNE-ŻYTKOW OBJECT)

The THORNE-ŻYTKOW object is described as a neutron star embedded within a red supergiant. It’s the cannibalism of the universe’s densest stars by the universe’s largest ones. 

In a binary system where two stars have a considerable difference in mass, it may occur that one of the stars quickly exhausts its fuel and ends up exploding as a supernova, leaving behind a neutron star corpse. If the other star is less massive and therefore evolves more slowly, at an earlier stage of compression it may become a red giant. During this process a sort of stellar cannibalism can occur in which the giant star devours the much smaller neutron star. 

This would not be a collision like in the case of a kilonova, since red giants are low-density stars and the neutron star could easily orbit inside the giant until it gets close to the core, by losing speed due to friction with the gaseous material of the red giant.

Ordinary red supergiants, like other stars, are powered by nuclear fusion in their cores. So when that energy runs out, their uncontested gravity causes them to implode before erupting as a supernova. But TZOs can live such long lives because they do not rely on sustained nuclear fusion in their cores to avoid collapse. Instead, a TZO’s neutron star core, which is already extremely compressed, largely prevents the rapid and uncontested gravitational collapse of the surrounding supergiant layers.

🔹 There are two main theories as to how the neutron star enters the belly of the red supergiant. It begins with a binary system where two stellar bodies are gravitationally bound together. The more massive of the two stars will explode into a supernova and give way to a neutron star. Over time, as the system evolves and the remaining red supergiant expands, the neutron star will spiral into the center of the supergiant where the neutron star will then be enveloped in a kind of hot, gaseous shell. 

Another scenario proposes that energy from a supernova shoots the neutron star towards the red supergiant where the two are then integrated with one another.

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