Unveiling the mysteries of black holes

Published: 

14 December 2018

The University of Southampton is part of international collaborations harnessing observations from the Japan Aerospace Exploration Agency and NASA’s X-ray space telescopes, NuSTAR and Hitomi, to better understand how black holes grow.

Black holes were first identified in space over 40 years ago, but we are still a long way from understanding how they grow and evolve. Dr Poshak Gandhi, Associate Professor and Science and Technology Facilities Council Ernest Rutherford Fellow in the University’s Astronomy Group, aims to change that. He is part of an international science team that has been developing and using the novel X-ray telescopes to achieve this.

So why study black holes? “Black holes are ubiquitous; every large galaxy hosts its own supermassive black hole at the centre,” says Poshak. “We now know that the growth of all these black holes goes hand-in-hand with the growth of the galaxies in which they sit: smaller black holes are hosted in smaller galaxies and larger galaxies tend to have much larger black holes.” There is now strong evidence to suggest that black holes have a much more profound impact on the Universe than once thought; galaxies themselves would have been much larger than they are today if black holes didn’t exist. Our own Milky Way galaxy may well have been much bigger than we see in the night sky.

As matter falls into black holes, it heats up to temperatures of many millions of degrees. This extreme environment is perfect for testing theories at the extremes of temperatures and gravity, which could not be achieved on Earth. The recent discovery of gravitational waves, in which Southampton researchers also participated, is a perfect example of the extreme physics that black holes allow us to probe.

While they are growing, black holes attract interstellar gas and dust, which radiates away its energy as it falls in, and can be detected using an X-ray telescope.