This experiment validated Einstein's theory of relativity
The star known as S0-2 is approaching the supermassive black hole Sagittarius A*, depicted in this illustration as a bottomless hole in the fabric of spacetime.
In 2019, the observation of the supermassive black hole located in the center of our galaxy made it possible to test once again the theory of general relativity published in 1915.
?What happens when a star passes near a supermassive black hole It offers astronomers the opportunity to test Einstein's theories.
By observing the behavior of a star orbiting the black hole at the center of our galaxy, scientists have confirmed that the intense gravitational field of this mysterious cosmic object has an effect on starlight , significantly delaying space travel. of its visitors. This observation is the best way to test a key prediction from Einstein's theory of general relativity , which suggests that light loses energy when it struggles to move through an extreme gravitational field.
"This type of experiment allows you to directly test how gravity works around a supermassive black hole," says Andrea Ghez , an astronomer at the University of California, Los Angeles, whose team reported the results in the science journal . “Gravity is extremely important, both for our understanding of the universe and for our daily lives. »
Astronomers hope to one day find proof that general relativity does not work in extreme gravitational environments, as this would pave the way for new types of physics that could solve some great mysteries in our understanding of the universe.
For the moment, however, it seems that Einstein was once again right and that other theories of gravity, including that developed by Isaac Newton, are ruled out.
A MASSIVE SET OF DATA
As Einstein described in his theory of general relativity, what we perceive as gravity is the result of an object's mass bending the fabric of spacetime. The theory also states that gravity affects everything, including light, and that very massive objects distort any light moving around them. This effect was notably observed during a solar eclipse in 1919 which made general relativity a pillar of science.
That's why astronomers are so excited about the presence of a group of stars orbiting the supermassive black hole at the center of our galaxy, a monster with a mass equivalent to four million suns called Sagittarius A*, or SgrA. *. It lies about 26,000 light-years from Earth, hidden behind a curtain of gas and dust.
The star in question is named S0-2 and orbits the Milky Way's supermassive black hole, completing an oval-shaped orbit in just 16 years. When in its course the star reaches its closest point to Sgr A*, the stars move through space at a speed of about 25 million kilometers per hour, or nearly 3% of the speed of the light.
Because its orbit is oval in shape, S0-2 oscillates between a more or less pronounced distance from the black hole Sgr A*. Ghez and his colleagues wanted to investigate the point at which S0-2 was closest to Sagittarius A*, last observed in May last year. So between March and September 2018, the team took precise measurements of stars moving through space using a series of telescopes in Chile and at the top of the Mauna Kea volcano in Hawaii.
"You really need to know, unambiguously, the shape of the orbit," says Ghez. “It's when it's closest to the black hole that the star experiences the strongest gravitational field, and you can test Einstein's theory of general relativity. »
The scientists added this new data to a wealth of observations collected since 1995; put together, this information allowed them to calculate the entire orbit of S0-2 in three dimensions.
SEE RED
To test the theory of general relativity, the team combined measurements of the star cluster's position in space with observations of its motion along Earth's line of sight to measure an effect called lag. gravitational red, or Einstein shift.
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