The gravitational redshift, caused by the extremely strong gravitational field, is clearly visible.
As it gets close to the black hole the 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.
Using highly advanced instruments in the Very Large Telescope at the European Southern Observatory in Chile, Genzel's team were able to see through the dusty veil and take infrared and near-infrared measurements of S2.
By following a distant star as it moved around the black hole, astronomers were able to measure the difference in wavelength of its light. The group of scientists has been observing a star in the Milky Way for a long time. This region, with the strongest gravitational field in our galaxy, is the ideal place to explore gravitational physics, and particularly to test Einstein's general theory of relativity.
But the numbers were in close agreement with predictions made using Einstein's theory of general relativity, revealing a phenomenon known as gravitational redshift in which light from S2 is stretched to longer wavelengths in the gravitational field of the black hole. In this graphic the colour effect, speed and size of the objects have been exaggerated for clarity.
Information was observed by and collected with the GRAVITY, SINFONI, and NACO instruments on ESO's Very Large Telescope (VLT). Genzel led a team that included collaborators worldwide from the Paris Observatory-PSL, the Université Grenoble Alpes, CNRS, the Max Planck Institute for Astronomy, the University of Cologne, the Portuguese CENTRA - Centro de Astroﬁsica e Gravitação and ESO.
In this case, it's a star named S2 that is in a 16-year orbit around the black hole.
This is the first time that this effect is measured for the gravitational field of a black hole.
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.
"This is the second time that we have observed the close passage of S2 around the black hole in our galactic centre. But this time, because of much improved instrumentation, we were able to observe the star with unprecedented resolution", explained in a statement Reinhard Genzel of the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany, the leader of ESO's worldwide team.
Last May, Genzel and his team pointed their instruments to S2 as it passed close to the black hole.
"And the change in the wavelength of light from S2 agrees precisely with that predicted by Einstein's theory of general relativity". The redshift was exactly what Einstein predicted it would be in the theory of relativity.
A team of worldwide scientists observing a star in the Milky Way have for the first time confirmed Einstein's predictions of what happens to the motion of a star passing close to a supermassive black hole. Astronomers use Gravity to make extraordinarily precise measurements of the changing position of S2, and thus also of the shape of its orbit. In previous times, when S2 came close to the black hole, that is, in 2002, the telescopes did not have enough resources for such detailed research.
The scientists now hope to observe other theories of black hole physics.
The very close passage happened on may 19. Jansky wanted to investigate further to find out why radio waves were coming from interstellar space, but Bell Labs was not interested, and no one else followed up on the discovery for several years.