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First successful test of Einstein's general relativity near
supermassive black hole (Update)
ESO
phys.org
Thursday, July 26, 2018
[Caption] This artist's impression shows the path of the
star S2 as it passes very close to the supermassive black
hole at the centre of the Milky Way. As it gets close to
the black hole the very strong gravitational field causes
the colour of the star to shift slightly to the red, an
effect of Einstein's general thery of relativity. In this
graphic the colour effect and size of the objects have been
exaggerated for clarity. Credit: ESO/M. Kornmesser
Observations made with ESO's Very Large Telescope have for
the first time revealed the effects predicted by Einstein's
general relativity on the motion of a star passing through
the extreme gravitational field near the supermassive black
hole in the centre of the Milky Way. This long-sought
result represents the climax of a 26-year-long observation
campaign using ESO's telescopes in Chile.
Obscured by thick clouds of absorbing dust, the closest
supermassive black hole to the Earth lies 26 000 light-
years away at the centre of the Milky Way. This
gravitational monster, which has a mass four million times
that of the Sun, is surrounded by a small group of stars
orbiting around it at high speed. This extreme environment
-- the strongest gravitational field in our galaxy -- makes
it the perfect place to explore gravitational physics, and
particularly to test Einstein's general theory of
relativity.
New infrared observations from the exquisitely sensitive
GRAVITY, SINFONI and NACO instruments on ESO's Very Large
Telescope (VLT) have now allowed astronomers to follow one
of these stars, called S2, as it passed very close to the
black hole during May 2018. At the closest point this star
was at a distance of less than 20 billion kilometres from
the black hole and moving at a speed in excess of 25
million kilometres per hour -- almost three percent of the
speed of light.
The team compared the position and velocity measurements
from GRAVITY and SINFONI respectively, along with previous
observations of S2 using other instruments, with the
predictions of Newtonian gravity, general relativity and
other theories of gravity. The new results are inconsistent
with Newtonian predictions and in excellent agreement with
the predictions of general relativity.
[Caption] This diagram shows the motion of the star S2
around the supermassive black hole at the centre of the
Milky Way. It was compiled from observations with ESO
telescopes and instruments over a period of more than 25
years. The star takes 16 years to complete one orbit and
was very close to the black hole in May 2018. Note that the
sizes of the black hole and the star are not to scale.
Credit: ESO/MPE/GRAVITY Collaboration
These extremely precise measurements were made by an
international team led by Reinhard Genzel of the Max Planck
Institute for Extraterrestrial Physics (MPE) in Garching,
Germany, in conjunction with collaborators around the
world, at the Paris Observatory–PSL, the Université
Grenoble Alpes, CNRS, the Max Planck Institute for
Astronomy, the University of Cologne, the Portuguese CENTRA
-- Centro de Astro?sica e Gravitação and ESO. The
observations are the culmination of a 26-year series of
ever-more-precise observations of the centre of the Milky
Way using ESO instruments.
"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," explains Genzel. "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."
The new measurements clearly reveal an effect called
gravitational redshift. Light from the star is stretched to
longer wavelengths by the very strong gravitational field
of 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. This is the first
time that this deviation from the predictions of the
simpler Newtonian theory of gravity has been observed in
the motion of a star around a supermassive black hole.
Continues at:
https://phys.org/news/2018-07-gravity-relativity-galactic-centre-massive.html
Jai Maharaj, Jyotishi
Om Shanti
http://groups.google.com/group/alt.fan.jai-maharaj
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