This Dancing Star Around The Black Hole Proves Einstein Was Right All Along

This Dancing Star Around The Black Hole Proves Einstein Was Right All Along

Astronomers were able to observe a star orbiting a massive black hole for the first time and it backed up Albert Einstein's general theory of relativity.

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Cover Image Source: ScienceSprings

It is the first time that astronomers have observed a star orbiting a supermassive black hole present at the centre of our Milky Way galaxy. Using the European Southern Observatory's Very Large Telescope in Chile's Atacama Desert, astronomers were able to make observations of the star whose orbit was shaped like a rosette. The study, published in the journal Astronomy & Astrophysics on Thursday, saw Albert Einstein's predicted general theory of relativity come to life. The shape of the orbit goes against Isaac Newton's theory of gravity which suggested that the trajectory would look like an ellipse. Meanwhile, it holds up Einstein's theory of relativity which proposed the rosette shape.


Reinhard Genzel, the director at the Max Planck Institute for Extraterrestrial Physics in Garching, Germany, explained the same in a statement, according to CNN. "Einstein's general relativity predicts that bound orbits of one object around another are not closed, as in Newtonian gravity, but precess forwards in the plane of motion," he said. A program demonstrating this outcome was led by Genzel. According to the outlet, it took over a 30-year period for the initiative to derive this precise measurement. Describing how the effect was seen previously in the orbit of planet Mercury, Genzel added, "This famous effect -- first seen in the orbit of the planet Mercury around the Sun -- was the first evidence in favor of general relativity."


"One hundred years later we have now detected the same effect in the motion of a star orbiting the compact radio source Sagittarius A* at the center of the Milky Way. This observational breakthrough strengthens the evidence that Sagittarius A* must be a supermassive black hole of 4 million times the mass of the sun," he continued. So, Sagittarius A* is the supermassive black hole present at the center of our galaxy and is 26,000 light-years away from the sun. To help you gauge better, our solar system exists on the edge of one of the Milky Way's massive spiral arms.


The black hole is densely surrounded by stars and one of them named S2 (in this observation) passes closest to the black hole within less than 20 billion kilometers. When it nears the black hole, it moves at 3% the speed of light so it takes 16 Earth years for S2 to complete an orbit around the black hole. "After following the star in its orbit for over two and a half decades, our exquisite measurements robustly detect S2's Schwarzschild precession in its path around Sagittarius A*," explained Stefan Gillessen, who led the analysis of the measurements at the Max Planck Institute for Extraterrestrial Physics. 


Now, orbits don't usually follow a perfectly circular path as the object either move closer or further away during rotation. S2's closest approach of the black hole keeps changing every time, thus creating the rosette shape. The theory of general relativity comes into play while predicting how much that orbit changes. Einstein's theory also allows us to understand the general area present at the center of our galaxy better as its difficult for us to observe it from such a distance due to the presence of gas and dust in our galaxy. The team, who previously reported the manner in which star's light stretches as it approaches the black hole, made the discovery possible by their dedicated observations of the stars over the period of 27 years. 


"Our previous result has shown that the light emitted from the star experiences general relativity. Now we have shown that the star itself senses the effects of general relativity," said study co-author Paulo Garcia who is a researcher at Portugal's Centre for Astrophysics and Gravitation. The future telescope European Southern Observatory's Extremely Large Telescope will allow them to observe fainter stars that move even closer to the black hole. "If we are lucky, we might capture stars close enough that they actually feel the rotation, the spin, of the black hole," said study co-author and project lead scientist from Cologne University in Germany Andreas Eckart. "That would be again a completely different level of testing relativity."


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