Most detailed observations of material orbiting close to a Black Hole

ESO’s GRAVITY instrument confirms black hole status of the Milky Way center.

Simulation of Material Orbiting close to a Black Hole
Simulation of Material Orbiting close to a Black Hole

ESO Gravity is a four-way beam combination second generation instrument for the VLTI. Its main operation mode makes use of all four 8m Unit Telescopes to measure astrometric distances between objects located within the 2” field-of-view of the VLTI.

The instrument now has added further evidence suggesting that a supermassive black hole lurks in the center of the Milky Way. It shows that bunches of gas twirling around at around 30% of the speed of light on a circular circle simply outside its event horizon.

This is for the first time that the material has been observed revolving near the point of no return, and the most detailed observations yet of material orbiting this close to a black hole.

The observed flares give hotly anticipated affirmation that the object in the focal point of our world is, as has for quite some time been accepted, a supermassive black hole. The flares start from material circling near the black hole’s event horizon — mentioning these the most detailed observations yet of material circling this near a black hole.

Wide-field view of the centre of the Milky Way
Wide-field view of the centre of the Milky Way

While some matter in the gradual accretion disc — the belt of gas circling Sagittarius A* at relativistic speed — can circle the black hole securely, anything that gets excessively close is bound to be pulled past the event horizon. The nearest point to a black hole that material can circle without being compellingly drawn inwards by the massive mass is known as the innermost stable orbit, and it is from here that the observed flares begin.

Oliver Pfuhl, a scientist at the MPE said, “It’s mind-boggling to actually witness material orbiting a massive black hole at 30% of the speed of light. GRAVITY’s tremendous sensitivity has allowed us to observe the accretion processes in real time in unprecedented detail.”

The GRAVITY instrument which made this work possible combines the light from four telescopes of ESO’s VLT to create a virtual super-telescope 130 meters in diameter, and has already been used to probe the nature of Sagittarius A*.

The centre of the Milky Way*
The centre of the Milky Way*

Pfuhl aid, “We were closely monitoring S2, and of course, we always keep an eye on Sagittarius A*. During our observations, we were lucky enough to notice three bright flares from around the black hole — it was a lucky coincidence!”

This emission, from highly energetic electrons very close to the black hole, was visible as three prominent bright flares and exactly matches theoretical predictions for hot spots orbiting close to a black hole of four million solar masses. The flares are thought to originate from magnetic interactions in the very hot gas orbiting very close to Sagittarius A*.

This research was presented in the journal Astronomy & Astrophysics on 31 October 2018.