Published: Sun, July 29, 2018
Research | By Jennifer Evans

Epic campaign confirms relativity near supermassive black hole

Epic campaign confirms relativity near supermassive black hole

According to the researchers, these conditions are extreme enough for the star to suffer the effects of general relativity.

This artist's impression provided by the European Southern Observatory in July 2018 shows the path of the star S2 as it passes close to the supermassive black hole at the center of the Milky Way galaxy.

It's predicted by Einstein's theory of general relativity, but has never been observed in an intense gravitational field such as that of a black hole. "But this time, because of much improved instrumentation, we were able to observe the star with unprecedented resolution".

Previously, scientists have proven that Einstein's explanation of how the universe works stands in the face of highly dense neutron stars and mysterious particles called ghost neutrinos. One of these stars, known as S2, has an elongated orbit with a period of 16 years and is suitable to the black hole at a distance of only 17 light hours (about 20 billion kilometers). As the star gets nearer to the black hole, a very strong gravitational field causes the color of the star to shift slightly to the red, an effect of Einstein's general theory of relativity.

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"We have put enormous effort into getting the instruments into good shape before the star approached the black hole", said Thibaut Paumard, a researcher at the French National Research Institute, the CNRS, in Paris.

This time-lapse view shows images from the GRAVITY instrument on ESO's Very Large Telescope as it tracks the progress of the star S2 as it made a close passage past the black hole at the centre of the Milky Way in May 2018. "So it's very important in astronomy to also check that those laws are still valid where the gravitational fields are very much stronger", said Françoise Delplancke, head of the System Engineering Department at ESO.

"We have been preparing intensely for this event over several years, as we wanted to make the most of this unique opportunity to observe general relativistic effects", added Genzel. Thus, the precise measurements of the position of the star allowed the scientists to highlight the effect of gravitational reddening predicted by the theory of Einstein.

The group of scientists started to monitor the central area of the Milky Way at the European Southern Observatory 26 years ago. The star got close to a monstrous black hole.

The team compared S2's position and velocity measurements to previous observations and found the results to be in agreement with Einstein's gravity predictions.

The scientists selected one star, S2, to follow. What they observed is the phenomenon of light waves, as they escape the strong gravitational field of the black hole, being stretched, which makes the light itself redder.

More than 100 years after he published his paper setting out the equations of general relativity, Einstein has been proved right once more - in a much more extreme laboratory than he could have possibly imagined. At the time of Einstein, he could not think or dream of what we are showing today.

This is the first time observers have been able to measure such an effect. The detection of changes in the trajectory of the star under the effect of gravity is expected in a few months and could provide information on the mass distribution around the black hole.

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