Its extremely strong gravitational field influences the surrounding area and has an impact on the motion of stars passing by.
"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", says Genzel. They also used GRAVITY instrument in the VLT Interferometer (VLTI) that unveils the motion of the star from night to night as it passes close to the black hole. his long-sought result represents the climax of a 26-year-long observation campaign using ESO's telescopes in Chile. 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.
They were using their Very Large Telescope to observe the motion of stars near the super-massive black hole.
German-born theoretical physicist's 100-year-old general theory of relativity predicted that light from stars would be stretched to longer wavelengths by the extreme gravitational field of a black hole, and the star would appear redder. In this graphic the colour effect and size of the objects have been exaggerated for clarity. Frank Eisenhauer, also from the Max Planck Institute for Extraterrestrial Physics. Goes around it a few stars, the orbits of which are known to astronomers and for those that watch closely for more than 20 years. When the star was only 120 times the Earth-Sun distance of Sgr A*, its orbital speed reached 8000 km/s or 2.7% of the speed of light. It takes about 15 years to complete its full orbit.
This is the first time that this effect is measured for the gravitational field of a black hole. European researchers reported the results of their observations in the journal Astronomy & Astrophysics on Thursday, July 26, 2018.
They then compared their measurements, along with previous observations of S2 using other instruments, with the predictions of Newtonian gravity, general relativity and other theories of gravity.
"This is the second time that we have observed the close passage of S2 around the black hole in the Galactic center", said Dr. Reinhard Genzel, from the Max Planck Institute for Extraterrestrial Physics in Germany.
However, Einsteins' theory of relativity doesn't explain everything about the universe so it comes down on scientists that they keep testing it time and again.
Astronomers followed S2 before and after it passed close to the black hole on 19 May 2018, tracking its progress hour-by-hour.
Their measurements revealed an effect called gravitational redshift.
More information on this subject can be found in the research paper titled "Detection of the Gravitational Redshift in the Orbit of the Star S2 near the Galactic Centre Massive Black Hole", by the GRAVITY Collaboration.
The light distorted in a way which agrees with Albert Einsteins' theory.
A team of global scientists proved for the first time Einstein's predictions of what happens to the motion of a star passing close to a super-massive black hole.
Dr. Genzel and colleagues used ESO's SINFONI (Spectrograph for INtegral Field Observations in the Near Infrared) instrument to measure the velocity of S2 towards and away from Earth and the GRAVITY instrument to make extraordinarily precise measurements of the star's changing position in order to define the shape of its orbit.