PHOTOGRAPHING GHOSTS IN SPACE Set with the virtually impossible task of photographing a black hole in space, 55 million light years from Earth, a group of scientists went to unprecedented lengths to overcome this challenge. SHAUN SMILLIE
SHIVAN PARUSNATH
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lack holes are probably some of the most mysterious, scary and fascinating phenomena in space. These dark lords of the cosmos have the power to give birth to or destroy stars – or even prevent them from forming. Being invisible, they pose a challenge to find, and an even bigger challenge to photograph. A multinational team of 300 scientists put their minds together to find their way around the problem: how do you photograph an object that is 55 million light years away, that you are not even able to see? The team included Wits Professor Roger Deane, South African Radio Astronomy Observatory (SARAO)/National Research Foundation Chair in Radio Astronomy and Wits/ SARAO postdoctoral fellow, Dr Iniyan Natarajan – the only two scientists from Africa that were part of the collaboration. Black holes are regions of spacetime where gravity is so strong that nothing can escape from them – even light. The gravity is so strong because large amounts of matter is squeezed into a tiny space, creating an extremely dense body. This can happen when a star is dying, or is found at the dense centre of a galaxy.
MATHEMATICAL MYSTERIES
As the gravity is so strong, black holes emit no light. They have been mathematical mysteries since Albert Einstein published his theory of general relativity. According to this theory, a sufficiently compact mass can deform spacetime to form a black hole. Black holes remained mere mathematical theories until the early 1970s. Then, several researchers independent of each other, identified the first black hole called Cygnus X-1, that is located about 6 070 light years from Earth. Over the past three decades it has become clear that black holes are not some fantastical interesting, exotic thought, but they actually influence the growth of our galaxies dramatically. “If a black hole gets all violent and angry, it can shut off all star formation in its galaxy. But it can also trigger some star formation,” says Deane. Research has shown that there is a clear correlation between the mass of a central black hole and the speed at which stars and gas move around within the galaxy. As black holes cannot be seen, scientists study the behaviour of objects – such as stars – around them to locate them. Each
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Astrophysicist Professor Roger Deane observes the South African night sky in front of the Wits Physics building.
