An international team of researchers, which includes 4 astronomers from the University of Amsterdam, has proven the existence of a gravitational vortex surrounding a black hole. This discovery explains a mystery that has perplexed astronomers for more than thirty years and effectively opens the way for theories to test gravitation. The team’s findings were published yesterday in the journal 'Monthly Notices of the Royal Astronomical Society'.
In the 1980s astronomers discovered that the X-rays emitted by black holes flicker. Such X-ray flickering is initially slow, about once every 10 seconds. In the days, weeks and months that follow, the flickering speeds up to about 10 times a second. The flickering then stops.
In the 1990s astronomers suspected that the flickering, also known as a quasi-periodic oscillation (QPO), might be linked to an effect predicted in Einstein’s Theory of General Relativity.
A rotating object should in theory be able to create a gravitational vortex, which can be compared to a spoon being stirred in a jar of honey. The spoon represents a black hole and the honey space. Everything in close proximity is caught up in the vortex caused by the black hole.
UvA researcher Adam Ingram has been investigating QPOs since 2009. Several years ago Ingram and fellow researchers came up with a theoretical explanation for this phenomenon, the proof for which has now been found. Ingram and his colleagues studied the black hole H1743-322 in the Scorpio constellation, about 28,000 light years from earth. They made their findings after 70 hours of observation with the ESA space telescope XMM-Newton and 20 hours with the NASA space telescope NuSTAR.
After analysing the data, the team identified shifts in the so-called iron line. These shifts could only be explained with the theory of the gravitational vortex
What’s great is that we can now directly measure the movement of matter in a strong gravitational field near a black hole’, says Ingram. ‘Moreover, we potentially have a new tool with which to test the general theory of relativity.’ The latter is something many astronomers and physicists have been working on in the suspicion that the theory of general relativity isn’t complete.
"A quasi-periodic modulation of the iron line centroid energy in the black hole binary H 1743-322." Adam Ingram (UvA), Michiel van der Klis (UvA), Matthew Middleton (Institute of Astronomy, Cambridge University), Chris Done (Center for Extragalactic Astronomy, Department of Physics, University of Durham), Diego Altamirano (Department of Physics & Astronomy, University of Southampton), Lucy Heil (UvA), Phil Uttley (UvA) & Magnus Axelsson (Department of Physics, Tokyo Metropolitan University), 12 juli 2016, Monthly Notices of the Royal Astronomical Society.