When a white dwarf star explodes like a supernova, can detonate like a nuclear weapon on Earth, finds a new study.
White dwarfs it is the faint, discolored cores, the size of the Earth, of the dead stars that are left behind after the medium-sized stars have exhausted their fuel and shed their outer layers. One day our sun will become a white dwarf, as will over 90% of the stars in our galaxy.
Previous research has found that white dwarfs can die in nuclear explosions known as type Ia supernovae. Much remains unknown about what triggers these explosions, but previous work has suggested that they may occur when a white dwarf buys extra fuel from a binary companion, probably due to a collision. (Instead, type II supernovae appear when a single star dies and collapses on its own).
Now researchers have suggested a new way for type Ia supernovae to happen – a white dwarf can detonate like a nuclear weapon.
Related: When will the sun die?
As a white dwarf cools, uranium and other heavy radioactive elements known as actinid crystallize in its core. Occasionally, the atoms of these elements spontaneously undergo nuclear fission, splitting into smaller fragments. These cases of radioactive decay can release energy and subatomic particles, such as neutrons, which can break nearby atoms.
If the amount of actinide in the core of a white dwarf exceeds a critical mass, it can trigger a chain reaction of explosive nuclear fission and flight. This explosion can then trigger nuclear fusion, with the nuclei of the atom fusing to generate huge amounts of energy. Similarly, a hydrogen bomb uses a nuclear fission chain reaction to detonate a nuclear fusion explosion.
The calculations of the new study and computer simulations found that a critical mass of uranium can indeed crystallize from the mixture of elements that are usually found in a refreshing white dwarf. If this uranium explodes due to a nuclear fission chain reaction, the scientists found that the resulting heat and pressure in the white dwarf’s core could be high enough to trigger the fusion of lighter elements, such as carbon and oxygen, resulting in the supernova.
“The conditions for building and detonating an atomic bomb seemed very difficult – I was surprised that these conditions could be met naturally in a very dense white dwarf,” said study co-author Charles Horowitz, a nuclear astrophysicist at Indiana University. , said Space.com. “If true, it offers a very new way of thinking about thermonuclear supernovae and maybe other astrophysical explosions.”
Photos Supernova: Great images of star explosions
So how many type Ia supernovae could explain this new mechanism? “Maybe about half,” Horowitz said.
Specifically, these new discoveries could explain type Ia supernovae that occur within a billion years of the formation of a white dwarf because their uranium has not yet completely fallen into radioactivity. When it comes to older white dwarfs, type Ia supernovae could happen through fusions of two white dwarfs, Horowitz said.
Future research may include performing computer simulations to determine whether fission chain reactions in white dwarfs can trigger fusion and how this happens. “There are many different physical processes during the explosion, and therefore there are many possible uncertainties,” Horowitz said. Such work could also reveal ways to detect whether or not any type of Ia supernova has occurred due to this new mechanism.
Horowitz and co-author of the study, Matt Caplan, a theoretical physicist at Illinois State University, detailed their discoveries online March 29 in Physical Review Letters.
Originally published on Space.com.