This causes a shift to the red end of the electromagnetic spectrum, a gravitational redshift
The same VLT was used to make the same observations back in 2016 when S2 passed by Sagittarius A* in 2016, however, they couldn't confirm Einstein's predictions as the instruments back then were not sensitive enough to detect the gravitational redshift
. "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," said the ESO in a statement.
Another solution of the gravitational redshift
is obtained with general relativity using the Schwarzschild metric.
This led him to his final discovery in the equivalence principle: a horizontal light pulse automatically looks slowed by the gravitational redshift
factor when watched from above  (see the last unnumbered equation on the last-but-second page).
Known as gravitational redshift
, the effect is caused by the black hole's powerful gravity, which slows time and causes light waves to lose energy.
Related to this is the gravitational redshift
, in which the wavelength of light from a massive object increases during the journey to the observer.
Cosmological Redshift Interpreted as Gravitational Redshift
. Progress in Physics, 2007, v.
Indeed, the more massive the hole, the greater this gravitational redshift
. So if the observatory's spectrometers can accurately measure the gravitational redshift
of X-rays emitted near a black hole, astronomers will be able to calculate the mass of the compact object that lurks there.
The Schwarzschild solution of the general relativity for a static spherically symmetric body predicts the perihelion precession of planets, the deflection of distant star light by the Sun, the gravitational redshift
of Sun's light, and the time delay of radar echoes, which have been well tested by the measurements [1-4].
He predicted two other effects, which were subsequently observed, namely the bending of starlight by the sun and the gravitational redshift
corresponding to the amount of energy light loses as it fights the effects of gravity.
Further applications to gravitational lensing , clusters of galaxies , the cosmological redshift as a gravitational redshift
, exoplanetary systems and the Kepler-16 circumbinary system  all support this QCM approach.