A white dwarf is not your typical star type.
While stars in the main sequence, such as our Sun, fuse nuclear material into their nuclei to prevent them from collapsing 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 gather electrons in the same state, they exert a degenerative pressure that prevents the white dwarf from collapsing.
But there is a limit to the amount of mass 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 Suns, gravity will crush the star into a neutron star or a black hole.
But Chandrasekhar’s limit is based on a fairly simple model. One in which the star is in balance and does not rotate. True white dwarfs are more complex, especially when subjected to 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 the end of their main sequence life, they become a binary system of white dwarfs.
Over time, their orbits can decompose, eventually causing the two white dwarfs to collide. What happens next depends on the situation.
They can often explode as a nova or supernova, creating a remaining neutron star, but sometimes they can form something more unusual, like a recent work in Astronomy and astrophysics shows.
In 2019, an X-ray source was discovered that looked similar to a white dwarf, but was too bright to be caused by a white dwarf. It has been suggested that the object may 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 has a mass greater than the Chandrasekar limit. The super-Chandrasekar object is surrounded by a remnant nebula with high wind speeds.
The nebula is mostly made of neon, seen as green in the image above. This is consistent with the object 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 in the next 10,000 years. It will probably create a supernova in this process. It seems that a white dwarf can break the Chandrasekhar limit, but only for a while.
This article was originally published by Universe Today. Read the original article.