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A unique star, careening around the monster black hole in the center of the Milky Way, provided astronomers with further evidence that Albert Einstein was right about gravity.
More than 100 years ago, Einstein's general theory of relativity this gravity is the result of the material that curves the fabric of space-time ( SN: 10 / 17/15, p.16 ). Now, in an article published July 26 in Astronomy & Astrophysics a team of researchers reports the observation of a sign of general relativity known as gravitational redshift. The measurement is the first time that general relativity has been confirmed in the region near a supermassive black hole.
As light escapes a region with a strong gravitational field, its waves expand, making the light more red. gravitational redshift. The scientists, a team known as the GRAVITY collaboration, used the Very Large Telescope Network, located in the Atacama Desert in Chile, to demonstrate that starlight was redshifted by the amount predicted by general relativity.
Gravitational redshift before. In fact, GPS satellites would not work properly if gravity redshift was not taken into account. But such effects have never been observed in the vicinity of a black hole where gravity is stronger. "It's completely new, and I think it's what makes it exciting – doing those same experiments not on Earth or in the solar system, but near a black hole," says the physicist Clifford Will of the University of Florida in Gainesville. with the new study
At the heart of the Milky Way lies a huge supermassive black hole, with a mass of about 4 million times that of the sun. Many stars swirl around this black hole ( SN Online: 1/12/18 ). The researchers pinpointed a star, known as S2, which completes an elliptical orbit around the black hole every 16 years
In May 2018, the star made its approach closest to the black hole, rising to 3 percent of the speed of light – extremely The star was only 20 billion kilometers from the black hole at that time, which may seem very distant, but only about four times the distance between the sun and Neptune. [19659002] Measuring the effects of general relativity in the vicinity of the black hole According to UCLA astronaut Tuan Do, who studies S2, but who has not participated in this work, if the we try to observe this region with an ordinary telescope, We'll see just this big blur. "
To obtain precise measurements and locate individual stars in the crowd, scientists used a technique called adaptive optics ( SN Online: 7/18/18 ), which can counteract distortion s caused by the Earth's atmosphere, and the combined information of our telescopes in the Very Large Telescope range. "You can gather light from these four telescopes and thus generate a super telescope … and that's the case," says Reinhard Genzel, co-author of the study, astrophysicist at the Max Planck Institute of extraterrestrial physics in Garching, Germany. Genzel and his colleagues have been observing this star for decades, before being swept by the black hole 16 years ago.
In a future work, scientists hope to test other aspects of general relativity, including the prediction of the S2 orbit. turn in time. A similar rotation has already been observed in the orbit of Mercury around the sun, which puzzled astronomers until Einstein's theory explains the effect ( SN Online: 4/11/18 ). orbit even closer to the black hole, which allows them to better understand the black hole and to examine more closely the general relativity. If this happens, Will will say, "They will really start exploring this black hole closely, and it will be a new series of tests of Einstein's theory."
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