When our Sun finally runs out of fuel and nears the end of its life, it will swell into a red giant before shedding its outer layer and shrinking into a white dwarf. This is the ultimate fate of most stars in the universe, which will reach the end of their evolution as white dwarfs.
Now, researchers from the WM Keck Observatory have discovered an unusual white dwarf, the smallest and most massive dwarf ever to exist. It is named J1901 + 1458 and lies relatively close, 130 light years from Earth.
This remarkable thing is that it “fills a mass greater than the mass of our sun into an object the size of our moon,” He said Lead author Ilaria Caiazzo of the California Institute of Technology. “This may seem counterintuitive, but the smaller white dwarfs are more massive. This is due to the fact that white dwarfs do not have the nuclear combustion that would allow normal stars to defy their own gravity, and instead their size is governed by quantum mechanics.”
Researchers believe that this white dwarf became so large because it was once part of a A pair of white dwarfs orbit each other. Eventually these two stars collided and merged into one heavier star. This process also increases the magnetic field around the star, making it spin faster. This white dwarf spins at a rotating speed, completing one cycle every seven minutes.
Because of their mass, these white dwarfs can then evolve into neutron stars, which are as dense as black holes and usually form from supernova explosions.
“This is highly speculative, but it is possible that the white dwarf is large enough to collapse further into a neutron star,” Chiazu said. It is so large and dense that electrons in its nucleus are captured by protons in the nucleus to form neutrons. Because the pressure of the electrons pushes against the force of gravity, which keeps the star intact, the core collapses when too many electrons are released.”
“We captured this very interesting object that wasn’t big enough to explode. We’re really investigating how massive the white dwarf is,” Chiazu said.
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