Calling someone a Hawking or a Zuckerberg or even a Jennings today doesn’t have the same effect as calling them an Einstein – even though Albert died in 1955 and never competed on Jeopardy. Einstein is still on the top of the genius pile because his brilliant theories continue to throw themselves into our faces and rub our noses into debunked theories to this day. Uncle Albert did it again just this week when astronomers using the ESO’s Very Large Telescope (VLT) found a star orbiting S2, the supermassive black hole at the center of the Milky Way, dances around it like a hokey-pokey rather than a circle dance. Can’t picture that? How about like a Swedish fried cookie rather than an Oreo? No? You’re obviously no Einstein.
“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. This famous effect — first seen in the orbit of the planet Mercury around the Sun — was the first evidence in favour 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 centre 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.”
“Precess forwards in the plane of motion,” according to Reinhard Genzel, Director at the Max Planck Institute for Extraterrestrial Physics in Germany and the leader of a 30-year study published in the journal Astronomy & Astrophysics, is how Einstein used his theory of General Relativity to rub Isaac Newton’s nose in his theory of gravity. In simple terms (finally!), most planets and stars have a non-circular elliptical orbit which moves them close to and then farther away from what they’re orbiting – as Newton predicts. However, new data on S2 shows that it “precesses” – that is, its closest point changes with each turn, so the next orbit is rotated with regard to the previous one, making it a shape like a deep-fried Swedish cookie known as the Rosette. Scientists too embarrassed to use such a simple simile call it the Schwarzschild precession named after the German astronomer Karl Schwarzschild) has never been measured for a star around a supermassive black hole … until now. Take that, Newtie! (Watch an excellent video of the orbit here.)
“Because the S2 measurements follow General Relativity so well, we can set stringent limits on how much invisible material, such as distributed dark matter or possible smaller black holes, is present around Sagittarius A*. This is of great interest for understanding the formation and evolution of supermassive black holes.”
In the press release announcing the study, French scientists Guy Perrin and Karine Perraut reveal how important this discovery is to those studying supermassive black holes. It’s not something that could have been determined in one observation, or even a year’s worth of them. Various astronomers watched S2 for 27 years of observations with the VLT’s instruments to record multiple years-long orbits. With what they have learned, astronomers hope to find stars orbiting even closer to Sagittarius A* and measure how it affects the space and time around it. Andreas Eckart from Cologne University, another scientist on the project, thinks Einstein would be pleased.
“That would be again a completely different level of testing relativity.”
In your face, Newtie!