spaceSpace and Physics

GRAVITY Instrument Prepares To Observe Our Galaxy's Black Hole


Jonathan O'Callaghan

Senior Staff Writer

619 GRAVITY Instrument Prepares To Observe Our Galaxy's Black Hole
Artist's impression of a supermassive black hole. NASA

A new instrument designed to observe regions near black holes is almost up and running – and we can expect its first spectacular views later this year. 

The instrument is called GRAVITY, and it has been installed on the European Southern Observatory’s (ESO) Very Large Telescope (VLT) in Chile. It creates a “virtual telescope” 200 meters (660 feet) across by combining light from multiple telescopes at the VLT site, via a process called interferometry.


GRAVITY will be used to study the extremely strong gravitational fields that exist close to the supermassive black hole at the center of our galaxy, named Sagittarius A*. Specifically, it will look towards the event horizon – the theoretical boundary to the inner black hole where gravity is so strong that nothing, not even light, can escape.

The instrument will also observe “mass accretion” around supermassive black holes, which is the process of material getting pulled in and swirling around in a superheated disc. GRAVITY will also be able to study this process occurring at newborn stars.

Where GRAVITY excels over other instruments is that it can make observations for several minutes, which is more than a hundred times longer than previously possible. “GRAVITY will open optical interferometry to observations of much fainter objects, and push the sensitivity and accuracy of high angular resolution astronomy to new limits, far beyond what is currently possible,” said Frank Eisenhauer of the Max Planck Institute for Extraterrestrial Physics in Germany, who led the installation of the instrument.

Shown is the GRAVITY instrument at the VLT in Chile. ESO/GRAVITY consortium


The instrument has already made its first observations, looking at the bright, young stars of the Trapezium Cluster. And it even made a discovery, finding that one component of the cluster was a previously unknown double star.

This observation was made using smaller telescopes at the VLT site, four 1.8-meter (6-foot) Auxilliary Telescopes. Later in 2016, it will use the four 8-meter (26-foot) VLT Unit Telescopes to start probing the regions near our supermassive black hole.

And this isn’t the only new black hole-hunting telescope. The Event Horizon Telescope, which will link nine telescopes from across the world, will also start observing Sagittarius A*, sometime in 2017. It is expected to get our first ever views of the black hole itself.


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