Using a catalog of 26,041 white dwarfs observed by the Sloan Digital Sky Survey, astronomers confirmed a long-predicted effect in these ancient, ultra-dense stars.
Concept art of two white dwarfs with the same mass but different temperatures. The hot star (left) is slightly swollen, while the cool star (right) is more compact. Image credit: Roberto Molar Candanosa / Johns Hopkins University.
At the end of their stellar evolution, stars that are not massive enough to become neutron stars or black holes eject their outer layers and leave their cores as compact remnants known as white dwarfs.
All stars with initial masses in the range of 0.07 to 8 solar masses (about 97% of all stars) end their lives as white dwarfs.
Dr Nicole Crumpler said: 'White dwarfs are a great way for us to work together to test theories underlying commonplace physics in the hope that we might discover something exotic that points to new fundamental physics. It is one of the best characterized stars ever made.” , an astrophysicist at Johns Hopkins University.
“If you want to look for dark matter, quantum gravity, and other unusual things, you need to have a good understanding of normal physics.”
“Otherwise, what seems novel may just be a new manifestation of an effect we already know.”
The new study was based on measurements of how these extreme conditions affect the light waves emitted by white dwarf stars.
As light moves away from such a huge object, it loses energy in the process of escaping gravity and gradually turns red.
This redshift effect stretches light waves like a rubber band so they can be measured with telescopes.
This is caused by the distortion of space-time caused by extreme gravity, as predicted by Einstein's theory of general relativity.
By averaging measurements of a white dwarf's motion with respect to Earth and grouping them according to gravity and size, astronomers can isolate gravitational redshifts to determine how high temperatures affect the volume of their gaseous outer layers. We measured the impact it had.
The team's 2020 study of 3,000 white dwarfs confirmed that electron degeneracy pressure causes stars to shrink as their mass increases. Electron degeneracy pressure is a quantum mechanical process that keeps dense nuclei stable for billions of years without the need for the nuclear fusion that normally underpins our sun and other planets. Types of stars.
“Until now, we haven't had enough data to confidently confirm the subtle but important effects of increasing temperature on the mass-size relationship,” Crumpler said.
“The next frontier may be detecting very subtle differences in the chemical composition of the cores of white dwarf stars of different masses,” said Dr. Nadia Zakamska, an astrophysicist at Johns Hopkins University.
“The maximum mass a star can have to form a white dwarf, as opposed to a neutron star or a black hole, is not completely understood.”
“These increasingly precise measurements will help test and refine theories about this and other poorly understood processes in the evolution of massive stars.”
“This observation could also help in attempts to discover signatures of dark matter, such as axions and other hypothetical particles,” Crumpler said.
“By providing a more detailed picture of the structure of white dwarfs, these data could be used to reveal the signals of certain models of dark matter that cause interference patterns in our galaxy.”
“If two white dwarfs are in the same dark matter interference patch, the dark matter will change the structure of these stars in the same way.”
Although dark matter has gravity, it does not emit light or energy that can be seen with telescopes.
Scientists have learned that the sun makes up most of the matter in the universe because its gravity affects stars, galaxies, and other space objects in the same way that it affects the orbits of planets. I am.
“We've been banging our heads against the wall trying to figure out what dark matter is, and I'd say we've been caught flat-footed,” Crumpler said.
“We know a lot about what dark matter is not, and there are limits to what dark matter can and cannot do, but we still don't know what it is.”
“That's why it's so important to understand simple objects like white dwarfs, because they give us hope of discovering what dark matter is.”
of study will appear in astrophysical journal.
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Nicole R. Crumpler others. 2024. Detection of temperature dependence of mass radius and gravitational redshift of white dwarfs. APJ 977, 237;doi: 10.3847/1538-4357/ad8ddc
Source: www.sci.news
