Nuclear fusion reactions are the process by which two lighter nuclei combine to release large amounts of energy, the process by which all the stars in the universe burn, while nuclear fission is the process by which heavier nuclei split to release large amounts of energy, like the mechanism of an atomic bomb explosion. Scientists generally agree that the latter is an extremely rare process within nature.
Recently, two scientists have proposed a new theory: not only are there natural nuclear fission reactions in stars, but it may also be that this triggers type 1a supernova explosions in the entire star.
When stars run out of Life, some become black holes, some become neutron stars, and some become white dwarfs. Now scientists have discovered that one of these white dwarfs may “die” again, in a Type 1a supernova explosion. The brightness of these supernovae is so stable that they are used by scientists as the “standard candle” in the universe to measure the rate of expansion of the universe.
The prevailing theory is that white dwarfs are able to undergo such supernova explosions because they are triggered by the action of companion stars. Beyond that, scientists can think of no other reason to “ignite” a white dwarf into a supernova explosion. The new study raises the possibility that a rare nuclear fission reaction could be the source.
The study by Charles Horowitz, a physics professor at Indiana University, and Matt Caplan, an assistant professor of physics at Illinois State University, suggests that a series of nuclear explosions may have been triggered by crystals of a radioactive material called uranium snowflakes on the white dwarf.
They speculate that about 100 million years after the star became a white dwarf, the white dwarf cooled enough to allow the actinides, or uranium analogs, inside to cool and crystallize.
“These crystals are very low in purity and may contain impurities such as lead and thorium, and may even be only half actinides and the other half light elements.” Kaplan explained their new research to Vice Media.
Within seconds, these strange crystals within a white dwarf star can expand to the size of a grain of sand. Because uranium is radioactive and unstable, a given nucleus could shoot three neutrons at its nearest neighbor, triggering a chain reaction of nuclear fission, similar to the mechanism of an atomic bomb explosion.
In this case, the resulting heat and energy would cause lighter elements, such as carbon and oxygen, to undergo fusion reactions, turning the white dwarf into a fusion bomb. This is like “detonating the largest nuclear bomb in the universe with the smallest nuclear bomb in the universe,” Kaplan said.
“Once there’s enough energy to burn all the carbon and oxygen in the star, the next thing you know, it’s like igniting a whole barrel of dynamite, and a supernova explosion happens that will completely destroy the star.”
In other words, Horowitz and Kaplan said, they believe it is possible to trigger a supernova explosion with just the decay of a single uranium nucleus. They say they have only proposed such a theory so far and hope that next, their peers will place such a hypothesis in various computer models to try and further investigate whether the heat from these uranium fissions would be enough to trigger a fusion reaction.
The Physical Review Letters accepted their study on Feb. 23 and will schedule it for publication. Preprint.arXiv has published the study on March 3.
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