Einstein's theory of general relativity passes black hole test

Einstein's theory of general relativity passes black hole test

Scientist were able to confirm the prediction of a theory, a phenomenon know as "gravitational redshifts"

It's when the wavelength of light gets stretched out in response to a gravitational field.

The Very Large Telescope (VLT) in Chile found evidence for Einstein's prediction by observing a star, called S2, that passed through the intense gravitational field of Sagittarius A* - the huge black hole at the heart of the Milky Way.
The effect they observed, gravitational redshift, occurs as particles of light (photons) climb out of a gravitational well like a black hole. As they do, the light's wavelength gets drawn out.

This shifts the wavelength to the red part of the light spectrum - hence "redshift".
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.

Astronomers got the result by tracking the movement of a star as it passed through the gravitational field of a black hole.

Frank Eisenhauer, from the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany, said the measurement opened the door to more studies of the physics of black holes. In future, he said, "we will see many more effects of general relativity in the galactic centre black hole. We will see the orbits of the stars change, we will see light go in circles, we will even see space-time rotate together with the black hole."

S2 is one member of a star cluster that surrounds Sagittarius A*. These stars reach mind-boggling speeds when they approach the black hole - S2 comes very close to Sagittarius A* every 16 years.
Astronomers followed S2 before and after it passed close to the black hole on 19 May 2018, tracking its progress hour-by-hour.
When S2 passed by the black hole at a distance just 120 times that of the Earth from the Sun, it reached an astonishing orbital velocity of 8,000 km/s. That corresponds to about 2.7% of the speed of light.
The astronomers found that light from the star was indeed stretched to longer wavelengths by the very strong gravitational field of Sagittarius A*.
The results were perfectly in line with the theory of general relativity - and not explained by Sir Isaac Newton's ideas - which exclude such a shift.
"In sport, you would say it was 1-0 for Einstein," said Frank Eisenhauer.

The astronomers are continuing to observe S2; observations of its trajectory should yield new findings about the extreme conditions around the Milky Way's central black hole.
Gravitational redshift occurs because, in order to escape a gravitational well such as a black hole, particles of light (photons) must expend energy.

Looking forward to a time when a time machine will be built so I can go back in time to meet that genius Albert Einstein.