At the heart of every white dwarf star is a dense stellar object left after the star burns its fuel reserves as it approaches its life cycle, there is quantum sophistication: when white dwarfs add mass, they shrink. size until they become so small and tightly compacted that they can no longer survive, collapsing into a neutron star.
This enigmatic mass-to-size ratio of the white dwarf, called the mass-to-radius ratio, was first theorized by Nobel Prize-winning astrophysicist Subrahmanyan Chandrasekhar in the 1930s. Johns Hopkins’ team of astrophysicists has now developed a method to observe the phenomenon itself, using astronomical data collected by the Sloan Digital Sky Survey and the latest data set released by the Gaia Space Observatory. The pooled datasets provided more than 3,000 white dwarfs for the team to learn.
A report of their findings, led by Hopkins senior Vedanta Chandra, is now in the press Astrophysical journal and available online arXiv.
“The mass-to-radius ratio is an impressive combination of quantum mechanics and gravity, but for us it is the opposite. We believe that the object is gaining mass and should become larger, ”says Nadia Zakamska, Associate Professor of Physics and Associate Professors. Astronomy, which supervised student researchers. “The theory has been around for a long time, but it is noteworthy that the data set we use is unprecedented in size and unprecedented accuracy. These measurement methods, which in some cases were developed many years ago, have suddenly become much better, and these old theories can finally be to check ’.
The team obtained its results using a combination of measurements, primarily including the gravitational redshift effect, which is the change in the wavelength of light from blue to red as the light moves away from the object. This is a direct result of Einstein’s general theory of relativity.
“The beauty of this work for me is that we all learn these theories about how light will be affected by gravity in school and textbooks, but now we actually see that relationship in the stars themselves,” says Hsiang, a fifth-year graduate. -Chih Hwang, who proposed the study and first recognized the effect of gravitational redshift in the data.
The team also had to account for how the movement of the star through space could affect its perception of gravitational redshift. Just as the siren of a fire engine changes the sound according to its movement relative to the listener, the frequency of the light also changes depending on the movement of the light emitting object relative to the observer. This is what the Doppler effect says, and is essentially a distracting “noise” that makes it difficult to measure the effect of gravitational redshift, says co-author Sihao Cheng, a fourth-year graduate student.
In order to take into account the changes caused by the Doppler effect, the team classified the white dwarfs in their sample by radius. They then calculated the redshifts of stars of similar size and effectively determined that no matter where the star itself is or where it moves relative to the Earth, some intrinsic gravitational redshift of a value can be expected to occur. Think of it as the average measurement of all the engine points of firefighters moving in a given place at a given time – you can expect the internal height of any fire engine, no matter which direction it moves, to be what the values are.
These internal values of gravitational redshift can be used to study the stars that will be observed in future datasets. The researchers say that future larger and more accurate data sets will allow further refinement of their measurements and that these data could help analyze the chemical composition of the white dwarf in the future.
They also say their research shows an interesting step from theory to observed phenomena.
“As the star becomes smaller as it becomes more massive, the effect of gravitational redshift increases with mass,” says Zakamska. “And it’s a little easier to understand – it’s easier to get out of a less dense, bigger object than to get out of a more massive, more compact object. That’s what we’ve seen in the data.”
The team even finds a captive audience for their research at home – where they did their work during the coronavirus pandemic.
“The way I raised it for my grandfather is that you basically see quantum mechanics and Einstein’s theory of general relativity to get that result,” Chandra says. “He was very excited when I said so.”
Astrophysicists confirm the cornerstone of Einstein’s theory of relativity
Gravitational redshift measurement of white dwarf mass to radius ratio, arXiv: 2007.14517 [astro-ph.SR] arxiv.org/abs/2007.14517
Presented by Johns Hopkins University
Citation: Astrophysicists observe long-theorized quantum phenomena (2020, July 30), derived from 2020. July 30 From https://phys.org/news/2020-07-astrophysicists-long-theorized-quantum-phenomena.html
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