Einstein’s theory of relativity has proven to be correct once again.
The first sign that Albert Einstein’s theory of gravity was correct has reappeared, this time near a supermassive black hole. In 1915, Einstein realized that his general theory of relativity explained a strange peculiarity in the orbit of Mercury. Now, that same effect has been identified in the orbit of a star in the huge black hole that inhabits the heart of the Milky Way.
The star, called S2, is part of a stellar entourage that surrounds the Milky Way’s central black hole, Sagittarius A * (located 25,640 light-years away from Earth). For decades, researchers have followed the elliptical motion of S2 around the black hole , taking precise measurements of the star’s position and velocity as it spins around the galactic center. The research team used the Very Large Telescope (VLT) of the European Southern Observatory (ESO) in Chile to track the star.
After watching the star complete almost two complete orbits (each complete orbit takes about 16 years), astronomers concluded that the star does not have a fixed elliptical orbit as predicted by Isaac Newton’s theory of gravity, but instead “dances” around of the black hole in a pattern that resembles a rosette drawn with a spirograph, as shown in the image.
This type of orbit, where the star’s closest point of approach moves subtly around the black hole with each orbit, is known as a Schwarzschild precession. It is like a spirograph drawing. That precession is the result of spacetime warping caused by massive objects, according to general relativity. Einstein predicted this type of unstable precession (or forward motion) more than 100 years ago to describe the effects of an infinitely small orbiting object on an extraordinarily massive one, the researchers wrote in their study in the journal Astronomy & Astrophysics.
“Einstein’s general relativity predicts that the bound orbits of one object around another are not closed, as in Newtonian gravity, but move forward in the plane of motion,” explained astrophysicist Reinhard Genzel of the Max Planck Institute for Physics. Extraterrestrial (MPE) in Germany, and a member of the GRAVITY Collaboration leading the study.
This is the first time that the Schwarzschild precession around a supermassive black hole has been detected, which shows that it is true even when we observe the orbits of stars in the most gravitationally extreme environment.
Also, the equations of general relativity can be used to accurately predict orbital changes, and these calculations have exactly matched the observations of S2. Thus, the observed precession exactly matched the predictions of general relativity, which could lead to new discoveries in the future, experts say.
“Because S2 measurements follow general relativity very well, we can set strict limits on how much invisible material , such as distributed dark matter or possible smaller black holes, is present around Sagittarius A *, which is great interest in understanding the formation and evolution of supermassive black holes, “the researchers added.
The theory of general relativity has not failed so far
While physicists have never found a case where general relativity is wrong, they are looking for cracks in the theory that may help lead to a new and improved theory of gravity.
Referencia: Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole, Astronomy & Astrophysics (2020). DOI: 10.1051/0004-6361/202037813 , https://www.aanda.org/articles … 3-20/aa37813-20.html
