Using a catalog of 26,041 white dwarfs observed by the Sloan Digital Sky Survey, astronomers have confirmed a long-predicted effect in these ancient ultradense stars.
Stars that are not massive enough to turn into neutron stars or black holes at the end of their stellar evolution expel their outer layers, leaving behind their cores as compact remnants known as white dwarfs.
All stars that have initial masses ranging from 0.07 to 8 solar masses, which is around 97% of all stars, end their lives as white dwarfs.
“White dwarfs are one of the best characterized stars that we can work with to test these underlying theories of run-of-the-mill physics in hopes that maybe we can find something wacky pointing to new fundamental physics,” said Dr. Nicole Crumpler, an astrophysicist at Johns Hopkins University.
“If you want to look for dark matter, quantum gravity, or other exotic things, you better understand normal physics.”
“Otherwise, something that seems novel might be just a new manifestation of an effect that we already know.”
The new research relied on measurements of how those extreme conditions influenced light waves emitted by white dwarfs.
Light traveling away from such massive objects loses energy in the process of escaping its gravity, gradually turning redder.
This redshift effect stretches light waves like rubber in ways telescopes can measure.
It results from the warping of spacetime caused by extreme gravity, as predicted by Einstein’s theory of general relativity.
By averaging measurements of the white dwarfs’ motions relative to Earth and grouping them according to their gravity and size, the astronomers isolated gravitational redshift to measure how higher temperatures influence the volume of their gaseous outer layers.
The team’s 2020 survey of 3,000 white dwarfs confirmed the stars shrink as they gain mass because of electron degeneracy pressure, a quantum mechanical process that keeps their dense cores stable over billions of…
Read the full article here
