Astronomers recently discovered a very dense white dwarf: the size of the moon is similar to the mass of the sun. The newly discovered white dwarf is the smallest and largest white dwarf ever, 130 light years away. Its age is estimated to be around 100 million years or less.
It seems illogical, but smaller white dwarfs are much more massive. The reason may be the lack of nuclear combustion that makes normal stars defy gravity, and instead their size is governed by quantum mechanics.
This smaller white dwarf is known as ZTF J1901 + 1458. It has a strong magnetic field one billion times stronger than ours. Sun‘s. What’s more, it rotates on its axis at high speed every seven minutes.
says Ilaria Caiazzo, a Sherman Fairchild postdoctoral researcher in theoretical astrophysics at Caltech, “We caught an extraordinary object that wasn’t big enough to explode. We’re really investigating how big the white dwarf is.”
Lots stars in the universe Spin each other in pairs. Stars age together, and if they are less than eight solar masses, both will evolve into white dwarfs.
The new study provides evidence of the next step beyond this stage: a pair of white dwarfs, orbiting each other, lose energy in the form of gravitational waves and eventually merge. If dead stars are large enough, they explode and form supernovae.
However, if it does not have a definite mass, it forms a solid white dwarf. This merger increases the star’s magnetic field and speeds up its rotation compared to its predecessor.
According to astronomers, compact white dwarfs may be large enough to evolve into neutron stars.
Caiazzo said, “This is highly speculative, but white dwarf It may be large enough to collapse further into a neutron star. They are so massive and dense that the electrons in their nucleus are captured by the 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.”
In the future, Caiazzo hopes to use ZTF to find more white dwarfs like this and, in general, to study the population as a whole.
Journal reference:
- Caiazzo, I., Burge, KB, Fuller, J. et al. A highly magnetic and rapidly rotating white dwarf as small as the moon. Nature 595, 39-42 (2021). DOI: 10.1038 / s41586-021-03615-y
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