Supermassive black holes were the focus in the second of a series of UKZN public lectures on astronomy and cosmology being hosted by the College of Agriculture, Engineering and Science’s Astrophysics and Cosmology Unit (ACRU).

The lecture was presented by South African-born Professor Anthony Readhead of the California Institute of Technology (CALTECH) in the United States.

Readhead has worked at Caltech since 1977 and is currently the Rawn Professor of Astronomy, Director of the Owens Valley Radio Observatory and a Senior Research Scientist at the Jet Propulsion Laboratory.

His interest in astronomy was sparked at an early age by the impressive Highveld night skies and he became an avid amateur astronomer, serving as a night assistant at the Ratcliffe observatory near Pretoria.

Readhead’s major scientific interests are active galaxies and the supermassive black holes that power them as well as cosmology, which is the study of the evolution of the universe.

He is a fellow of the US National Academy of Sciences and the American Academy of Arts and Sciences. 

In his public lecture titled Supermassive Black Holes:  A Fascinating Tale of Scientific Sleuthing, Readhead led a packed auditorium of interested academics, students, schoolchildren and members of the public through a condensed history of the major cosmological breakthroughs in the 20th century relating to black holes and the amazing phenomena they generate.

‘Near the core of our Milky Way galaxy, stars crowd together and the gas gets denser,’ said Readhead.  ‘At the core lies a supermassive black hole, with a mass larger than that of a million suns.  Gravity squeezes gas ever more densely to form a black hole from which nothing can escape, not even light.  Stars and gas near the centre of the galaxy risk being drawn into the black hole.’

Readhead said that in 1918 a strange jet-like feature was observed protruding from the nucleus of a distant giant galaxy in the constellation of Virgo. This was a complete mystery until 1963, when the first quasar was discovered and it too had a jet protruding from the nucleus.

Readhead explained that quasars were active galaxies with nuclei the size of the solar system that outshine 100 billion suns. The central engines in quasars are now known to be supermassive black holes, which eject matter in narrow jets along their spin axes at close to the speed of light.

‘Observations covering the whole electromagnetic spectrum from radio to gamma-ray energies, combined with computer simulations, reveal how the black holes accomplish this remarkable feat,’ said Readhead. ‘Now we have a very good idea of what is going on in the centres of galaxies, especially our own galaxy.’

Readhead said the final puzzle was to understand the motion of the stars around the black hole galactic centre.  ‘Theorists have devised competing scenarios.  Now we want to compare these scenarios with real objects.  We are at the most fascinating stage now where the observations can actually test things and put the final piece into the puzzle.’

Readhead played an instrumental role in South Africa’s successful bid for the Square Kilometre Array (SKA) radio telescope.  He said he was impressed with the strategic focus on cosmology and astrophysics and UKZN.  In particular, he liked ACRU’s outreach efforts and was hoping to implement similar initiatives at CALTECH. 

Dean and Head of the School of Mathematics, Statistics and Computer Science at UKZN, Professor Kesh Govinder, confirmed that the two institutions would be initiating a number of joint projects.

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