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Pythagorean Astronomy: The Origins of Black Holes

Chris North

30 June 2016

GRO J1655-40 is the second so-called 'microquasar' discovered in our Galaxy. Microquasars are black holes of about the same mass as a star. They behave as scaled-down versions of much more massive black holes that are at the cores of extremely active galaxies, called quasars. Astronomers have known about the existence of stellar-mass black holes since the early 1970s. Their masses can range from 3.5 to approximately 15 times the mass of our Sun. Using Hubble data, astronomers were able to describe the black-hole system. The companion star had apparently survived the original supernova explosion that created the black hole. It is an ageing star that completes an orbit around the black hole every 2.6 days. It is being slowly devoured by the black hole. Blowtorch-like jets (shown in blue) are streaming away from the black-hole system at 90% of the speed of light.

Artist’s Impression of a black hole in a binary star system. Credit: ESA/Hubble

On 15th June 2016 the LIGO collaboration released more detections of gravitational waves. As with the first detection, announced back in February, these gravitational waves were emitted by pairs of black holes, spiralling together and merging,

But of course, those black holes need to come from somewhere, and in this case it’s thought to be the deaths of some of the most massive stars in the Universe. To understand more about the deaths of massive stars, and the formation of black holes, I talked to Professor Stephen Smartt, from Queen’s University Belfast, who’s been on the hunt for black holes.

Originally broadcast on 30th June 2016 as part of Pythagoras’ Trousers on Radio Cardiff.