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Successful first observations of the galactic centre with GRAVITY

Jun. 23, 2016

The Black hole probe is now working with the four VLT Unit Telescopes.

A European team of astronomers, including portuguese researchers from CENTRA, have used the new GRAVITY instrument at ESO’s Very Large Telescope to obtain exciting observations of the centre of the Milky Way by combining light from all fourof the 8.2-metre Unit Telescopes for the first time.

These results provide a taste of the groundbreaking science that GRAVITY will produce as it probes the extremely strong gravitational fields close to the 4 million solar mass black hole at the centre of our galaxy, and tests Einstein’s general relativity under extreme conditions.

GRAVITY is part of the VLT Interferometer. By combining light from the four 8.2-meter telescopes it can achieve the same spatial resolution and precision in measuring positions as a telescope of up to 130 metres in diameter. CENTRA’s team contribution was to build the instrument acquisition camera, a subsystem that tracks the scientific target on the sky and obtains critical optical information from light beams, allowing the instrument to achieve its exceptional precision in the position of an astronomical object.

The team will soon be able to obtain ultra-precise positions equivalent to measuring the position of an object on the Moon with centimetre precision. That will enable them to determine whether the motion of the stars around the black hole follows thepredictions of Einstein’s general theory of relativity — or not.

In 2018 one of these stars will be at its closest to the black hole, just 17 light-hours away from it and travelling at almost 30 million kilometres per hour, or 2.5% of the speed of light. At this distance the effects due to general relativity will be most pronounced and GRAVITY observations will yield their most important results. This opportunity will not be repeated for another 16 years.

Check the full press release at the ESO site.


The GRAVITY consortium is led by the Max Planck Institute for Extraterrestrial Physics, in Garching, Germany. The other partner institutes are:

• LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité,Meudon, France

• Max Planck Institute for Astronomy, Heidelberg, Germany

• Physikalisches Institut, University of Cologne, Cologne, Germany

• IPAG, Université Grenoble Alpes/CNRS, Grenoble, France

• Centro Multidisciplinar de Astrofísica, CENTRA (SIM), Lisbon and Oporto, Portugal

• ESO, Garching, Germany