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A star orbiting a black hole again proved Einstein right about Gravity


A single star, orbiting around the monster black hole in the center of the Milky Way, which again proved that Albert Einstein was right about gravity. More than 100 years ago, Einstein’s general theory of relativity revealed that gravity is the result of matter curving the fabric of spacetime.

As light escapes from a region with a strong gravitational field, its waves get stretched out, making the light redder, in a phenomenon known as gravitational redshift. A team of scientists, known as the GRAVITY collaboration, used the Very Large Telescope array, located in the Atacama Desert of Chile, to demonstrate that light from the star was redshifted by just the amount predicted by General Relativity.


Scientists have observed gravitational redshift before. In fact, GPS satellites would fail to function properly if gravitational redshift weren’t taken into account. But such effects have never been seen in the region of a black hole.

“That’s completely new, and I think that’s what makes it exciting — doing these same experiments not on Earth or in the solar system, but near a black hole.”

Clifford Will (Physicist) University of Florida, Gainesville.

The researchers observed that one star, known as S2, which completes an elliptical orbit around the black hole every 16 years, sitting at the heart of the Milky Way. Its speed is almost 3% of the speed of light.

In May 2018, the star made its closest approach to the black hole, zipping by at 3 percent of the speed of light — extremely fast for a star. At that point, the star was just 20 billion kilometers from the black hole. That may sound far away, but it’s only about four times the distance between the sun and Neptune.

To obtain precise measurements and pinpoint individual stars in the crowd, the scientists used a technique called Adaptive Optics, which can counteract the distortions caused by the Earth’s atmosphere, and combined information from four telescopes in the Very Large Telescope’s array.

The GRAVITY researchers might find other stars that orbit even closer to the black hole, allowing them to better understand the black hole and further scrutinize general relativity. If that happens, Will says, “they’ll really start to explore this black hole up close and personal, and it’ll be a very cool new set of tests of Einstein’s theory.”

This article was originally posted at ScienceNews
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