Scientists find evidence of Einstein's theory of general relativity in the cores of dead stars

Scientists find evidence of Einstein's theory of general relativity in the cores of dead stars
Scientists find evidence of Einstein's theory of general relativity in the cores of dead stars
Anonim

Scientists have supported Albert Einstein's theory of general relativity by exploring the strange mysteries of white dwarfs.

Astronomers have long assumed a relationship between the mass and radius of a white dwarf star, but until now could not observe the relationship between the mass and radius of the star, a new study shows. As white dwarfs gain mass, they decrease in size, unlike most of the known celestial objects.

In this new work, the researchers used a new method that included data from thousands of white dwarfs to observe the strange phenomenon and provide additional evidence for general relativity.

When stars like our Sun run out of fuel, they shed their outer layers and are exposed to an Earth-sized core. This core is known as a white dwarf and is believed to be the ultimate evolutionary state of the stellar object.

But these stellar remnants are fraught with a mystery, because when white dwarfs increase in mass, they decrease in size. Therefore, white dwarfs will eventually have a mass similar to that of the Sun, but packed into a body the size of the Earth.

White dwarfs become so small and compact that they eventually disintegrate into neutron stars, very dense stellar bodies with a radius that usually does not extend beyond 30 kilometers.

The strange relationship between mass and radius inside white dwarfs was theorized in the 1930s. The reason white dwarfs gain mass while contracting is believed to be due to the state of their electrons - when a white dwarf contracts, its electrons increase.

This mechanism is a combination of quantum mechanics - the fundamental theory in physics about the motion and interaction of subatomic particles and Albert Einstein's general theory of relativity, which deals with gravitational effects.

"The mass-to-radius ratio is an impressive combination of quantum mechanics and gravity, but for us it defies common sense," said Nadya Zakamskaya, associate professor in the Department of Physics and Astronomy at Johns Hopkins University, who led the new study. "We think that as an object gains mass, it should get bigger."

In this new study, a team at Johns Hopkins University developed a method for observing the mass-to-radius ratio in white dwarfs. Using data collected by the Sloan Digital Sky Survey and the Gaia Space Observatory, the researchers studied 3,000 white dwarfs.

The research team measured the gravitational redshift effect, which is the effect of gravity on light, on stars. As light moves away from an object, the wavelength of the light emanating from the object lengthens, making it appear redder. By studying the gravitational effect of redshift, they were able to determine the radial velocity of white dwarfs that have the same radius.

Radial velocity is the distance from the Sun to a given star, which determines whether a star is moving toward or away from the Sun. By determining the radial velocity of stars, they could also determine the change in the mass of stars.

"The theory has been around for a long time, but what is remarkable is that the dataset we used is of unprecedented size and unprecedented accuracy," Zakamska added. "These measurement methods, which in some cases were developed many years ago, suddenly work much better, and these old theories can finally be explored."

The method used in the study essentially turned theory into an observational phenomenon. In addition, it can be used to study more stars in the future and can help astronomers analyze the chemical composition of white dwarfs.

"As the star gets smaller as it gets more massive, the gravitational redshift also grows with mass," Zakamska said.

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