Artist’s impression of S2 passing supermassive black hole at centre of Milky Way - annotated
Orbit diagram of S2 around black hole at centre of the Milky Way
Orbits of stars around black hole at the heart of the Milky Way
The daily motion of the S2 star as seen with GRAVITY
GRAVITY tracks star passing supermassive black hole
NACO observation of the stars at the centre of the Milky Way
Videos
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.
The team used SINFONI to measure the velocity of S2 towards and away from Earth and the GRAVITY instrument in the VLT Interferometer (VLTI) to make extraordinarily precise measurements of the changing position of S2 in order to define the shape of its orbit. GRAVITY creates such sharp images that it can reveal the motion of the star from night to night as it passes close to the black hole — 26 000 light-years from Earth.
ESOcast 173: First Successful Test of Einstein’s General Relativity Near Supermassive Black Hole
Artist's impression of star passing close to supermassive black hole
Zooming in on the heart of the Milky Way
The star S2 makes a close approach to the black hole at the centre of the Milky Way
Stars orbiting the black hole at the heart of the Milky Way
Simulation of the orbits of stars around the black hole at the centre of the Milky Way
Animation of the orbit of the star S2 around the galactic centre black hole
Fulldome view of stars orbiting the black hole at the heart of the Milky Way
Orbiting a black hole near the event horizon (fulldome)
Close-up of a black hole near the event horizon (fulldome)
Orbiting a black hole near the event horizon 2 (fulldome)
Orbiting a black hole near the event horizon 3 (fulldome)
Orbiting a black hole near the event horizon 4 (fulldome)
Flight from the Earth to the Milky Way Black Hole
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 [1], 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
[2].
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.
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 Astrofisica 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 [3].
“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 team used SINFONI to measure the velocity of S2 towards and away from Earth and the GRAVITY instrument in the VLT Interferometer (VLTI) to make extraordinarily precise measurements of the changing position of S2 in order to define the shape of its orbit. GRAVITY creates such sharp images that it can reveal the motion of the star from night to night as it passes close to the black hole — 26 000 light-years from Earth.
“Our first observations of S2 with GRAVITY, about two years ago, already showed that we would have the ideal black hole laboratory,” adds Frank Eisenhauer (MPE), Principal Investigator of GRAVITY and the SINFONI spectrograph. “During
the close passage, we could even detect the faint glow around the black
hole on most of the images, which allowed us to precisely follow the
star on its orbit, ultimately leading to the detection of the
gravitational redshift in the spectrum of S2.”
More than one hundred 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!
Françoise Delplancke, head of the System Engineering Department at ESO, explains the significance of the observations: “Here
in the Solar System we can only test the laws of physics now and under
certain circumstances. So it’s very important in astronomy to also check
that those laws are still valid where the gravitational fields are very
much stronger.”
Continuing observations are expected to reveal another relativistic
effect very soon — a small rotation of the star’s orbit, known as Schwarzschild precession — as S2 moves away from the black hole.
Xavier Barcons, ESO’s Director General, concludes: “ESO
has worked with Reinhard Genzel and his team and collaborators in the
ESO Member States for over a quarter of a century. It was a huge
challenge to develop the uniquely powerful instruments needed to make
these very delicate measurements and to deploy them at the VLT in Paranal. The discovery announced today is the very exciting result of a remarkable partnership.”
Notes
[1] GRAVITY was developed by a collaboration consisting of
the Max Planck Institute for Extraterrestrial Physics (Germany), LESIA
of Paris Observatory–PSL / CNRS / Sorbonne Université / Univ. Paris
Diderot and IPAG of Université Grenoble Alpes / CNRS (France), the Max
Planck Institute for Astronomy (Germany), the University of Cologne
(Germany), the CENTRA–Centro de Astrofisica e Gravitação (Portugal) and
ESO.
[2] S2 orbits the black hole
every 16 years in a highly eccentric orbit that brings it within twenty
billion kilometres — 120 times the distance from Earth to the Sun, or
about four times the distance from the Sun to Neptune — at its closest
approach to the black hole. This distance corresponds to about 1500
times the Schwarzschild radius of the black hole itself.
[3] Observations of the
centre of the Milky Way must be made at longer wavelengths (in this case
infrared) as the clouds of dust between the Earth and the central
region strongly absorb visible light.
More Information
This research was presented in a paper entitled “Detection
of the Gravitational Redshift in the Orbit of the Star S2 near the
Galactic Centre Massive Black Hole“, by the GRAVITY Collaboration, to
appear in the journal Astronomy & Astrophysics on 26 July 2018.
The GRAVITY Collaboration team is composed of: R. Abuter
(ESO, Garching, Germany), A. Amorim (Universidade de Lisboa, Lisbon,
Portugal), N. Anugu (Universidade do Porto, Porto, Portugal), M. Bauböck
(Max Planck Institute for Extraterrestrial Physics, Garching, Germany
[MPE]), M. Benisty (Univ. Grenoble Alpes, CNRS, IPAG, Grenoble, France
[IPAG]), J.P. Berger (IPAG; ESO, Garching, Germany), N. Blind
(Observatoire de Genève, Université de Genève, Versoix, Switzerland), H.
Bonnet (ESO, Garching, Germany), W. Brandner (Max Planck Institute for
Astronomy, Heidelberg, Germany [MPIA]), A. Buron (MPE), C. Collin
(LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne
Universités, UPMC Univ. Paris 06, Univ. Paris Diderot, Meudon, France
[LESIA]), F. Chapron (LESIA), Y. Clénet (LESIA), V. Coudé du Foresto
(LESIA), P. T. de Zeeuw (Sterrewacht Leiden, Leiden University, Leiden,
The Netherlands; MPE), C. Deen (MPE), F. Delplancke-Ströbele (ESO,
Garching, Germany), R. Dembet (ESO, Garching, Germany; LESIA), J. Dexter
(MPE), G. Duvert (IPAG), A. Eckart (University of Cologne, Cologne,
Germany; Max Planck Institute for Radio Astronomy, Bonn, Germany), F.
Eisenhauer (MPE), G. Finger (ESO, Garching, Germany), N.M. Förster
Schreiber (MPE), P. Fédou (LESIA), P. Garcia (Universidade do Porto,
Porto, Portugal), R. Garcia Lopez (MPIA), F. Gao (MPE), E. Gendron
(LESIA), R. Genzel (MPE; University of California, Berkeley, California,
USA), S. Gillessen (MPE), P. Gordo (Universidade de Lisboa, Lisboa,
Portugal), M. Habibi (MPE), X. Haubois (ESO, Santiago, Chile), M. Haug
(ESO, Garching, Germany), F. Haußmann (MPE), Th. Henning (MPIA), S.
Hippler (MPIA), M. Horrobin (University of Cologne, Cologne, Germany),
Z. Hubert (LESIA; MPIA), N. Hubin (ESO, Garching, Germany), A. Jimenez
Rosales (MPE), L. Jochum (ESO, Garching, Germany), L. Jocou (IPAG), A.
Kaufer (ESO, Santiago, Chile), S. Kellner (Max Planck Institute for
Radio Astronomy, Bonn, Germany), S. Kendrew (MPIA, ESA), P. Kervella
(LESIA; MPIA), Y. Kok (MPE), M. Kulas (MPIA), S. Lacour (LESIA), V.
Lapeyrère (LESIA), B. Lazareff (IPAG), J.-B. Le Bouquin (IPAG), P. Léna
(LESIA), M. Lippa (MPE), R. Lenzen (MPIA), A. Mérand (ESO, Garching,
Germany), E. Müller (ESO, Garching, Germany; MPIA), U. Neumann (MPIA),
T. Ott (MPE), L. Palanca (ESO, Santiago, Chile), T. Paumard (LESIA), L.
Pasquini (ESO, Garching, Germany), K. Perraut (IPAG), G. Perrin (LESIA),
O. Pfuhl (MPE), P.M. Plewa (MPE), S. Rabien (MPE), J. Ramos (MPIA), C.
Rau (MPE), G. Rodríguez-Coira (LESIA), R.-R. Rohloff (MPIA), G. Rousset
(LESIA), J. Sanchez-Bermudez (ESO, Santiago, Chile; MPIA), S.
Scheithauer (MPIA), M. Schöller (ESO, Garching, Germany), N. Schuler
(ESO, Santiago, Chile), J. Spyromilio (ESO, Garching, Germany), O.
Straub (LESIA), C. Straubmeier (University of Cologne, Cologne,
Germany), E. Sturm (MPE), L.J. Tacconi (MPE), K.R.W. Tristram (ESO,
Santiago, Chile), F. Vincent (LESIA), S. von Fellenberg (MPE), I. Wank
(University of Cologne, Cologne, Germany), I. Waisberg (MPE), F. Widmann
(MPE), E. Wieprecht (MPE), M. Wiest (University of Cologne, Cologne,
Germany), E. Wiezorrek (MPE), J. Woillez (ESO, Garching, Germany), S.
Yazici (MPE; University of Cologne, Cologne, Germany), D. Ziegler
(LESIA) and G. Zins (ESO, Santiago, Chile).
ESO is the foremost intergovernmental astronomy
organisation in Europe and the world’s most productive ground-based
astronomical observatory by far. It has 15 Member States: Austria,
Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy,
the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the
United Kingdom, along with the host state of Chile and with Australia as
a strategic partner. ESO carries out an ambitious programme focused on
the design, construction and operation of powerful ground-based
observing facilities enabling astronomers to make important scientific
discoveries. ESO also plays a leading role in promoting and organising
cooperation in astronomical research. ESO operates three unique
world-class observing sites in Chile: La Silla, Paranal and Chajnantor.
At Paranal, ESO operates the Very Large Telescope and its world-leading
Very Large Telescope Interferometer as well as two survey telescopes,
VISTA working in the infrared and the visible-light VLT Survey
Telescope. ESO is also a major partner in two facilities on Chajnantor,
APEX and ALMA, the largest astronomical project in existence. And on
Cerro Armazones, close to Paranal, ESO is building the 39-metre
Extremely Large Telescope, the ELT, which will become “the world’s
biggest eye on the sky”.
Links
- Research paper in Astronomy & Astrophysics
- Preprint of paper in A&A
- Photos of the VLT
- GRAVITY webpages at the Max-Planck-Institut für extraterrestrische Physik
- MPE press release
- Successful first observations of the galactic centre with GRAVITY
Contacts
Reinhard Genzel
Director, Max Planck Institute for Extraterrestrial Physics
Garching bei München, Germany
Tel: +49 89 30000 3280
Email: genzel@mpe.mpg.de
Frank Eisenhauer
GRAVITY Principal Investigator, Max Planck Institute for Extraterrestrial Physics
Garching bei München, Germany
Tel: +49 (89) 30 000 3563
Email: eisenhau@mpe.mpg.de
Stefan Gillessen
Max-Planck Institute for Extraterrestrial Physics
Garching bei München, Germany
Tel: +49 89 30000 3839
Email: ste@mpe.mpg.de
Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: pio@eso.org
Hannelore Hämmerle
Public Information Officer, Max Planck Institute for Extraterrestrial Physics
Garching bei München, Germany
Tel: +49 (89) 30 000 3980
Email: hannelore.haemmerle@mpe.mpg.de
Source: ESO/News
