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A white dwarf is not your typical type of star.
While main sequence stars such as our Sun fuse nuclear material in their nuclei so as not to collapse under their own weight, white dwarfs use an effect known as quantum degeneration. The quantum nature of electrons means that no electron can have the same quantum state.
When you try to push electrons in the same state, they exert degenerative pressure which prevents the white dwarf from collapsing.
But there is a limit to the mass that a white dwarf can have.
Subrahmanyan Chandrasekhar made a detailed calculation of this limit in 1930 and found that if a white dwarf has more mass than about 1.4 Sun, gravity will crush the star into a neutron star or black hole.
But the Chandrasekhar limit is based on a fairly simple model. The one where the star is in equilibrium and does not rotate. True white dwarfs are more complex, especially when experiencing collisions.
Binary white dwarfs are quite common in the universe. Many sun-like stars and red dwarfs are part of a binary system.
(ESA / XMM-Newton, L. Oskinova / Univ. Potsdam, Germany)
When these stars reach, they reach the end of their life in the main sequence, they become a binary system of white dwarfs.
Over time, their eye sockets can disintegrate, eventually causing the two white dwarfs to collide. What happens next depends on the situation.
Often times they can explode in nova or supernova creating a residual neutron star, but sometimes they can form something more unusual, like a recent article in Astronomy and astrophysics shows.
In 2019, an x-ray source was discovered that looked like a white dwarf but was too bright to be caused by a white dwarf. It has been suggested that the object could be an unstable fusion of two white dwarfs. In this new study, a team used the XMM-Newton X-ray telescope to capture an image of the object, seen above.
They confirmed that the object had a mass greater than the Chandrasekar limit. The super-Chandrasekar object is surrounded by a remaining nebula with high wind speeds.
The nebula is mostly made of neon, seen in green in the image above. This is consistent with the fact that the object was created by a white dwarf fusion. It probably has a high rotation, which prevents the object from collapsing into a neutron star.
Eventually, this object will collapse to become a neutron star within the next 10,000 years. This will likely create a supernova in the process. It seems that a white dwarf can break the Chandrasekhar boundary, but only for a while.
This article was originally published by Universe Today. Read the original article.
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