PUNE: Using four telescopes including the Giant Metrewave Radio Telescope (GMRT) in Pune, astronomers have discovered the biggest explosion seen in the universe since the Big Bang.
The blast, which released five times more energy than the previous record holder, came from a supermassive black hole at the centre of a galaxy hundreds of millions of light years away.
The other telescopes used for the discovery included NASA’s Chandra X-ray Observatory, European Space Agency’s (ESA) XMM-Newton and the Murchison Widefield Array (MWA) in Western Australia.
Meanwhile, the radio data from the GMRT played an important role in helping to unravel the mystery about the nature of this explosion. The data was taken in 2008 and was available in the observatory archive and reanalysed by the international team of researchers to get an improved radio image of the radio source, as seen by the GMRT.
It complemented very nicely with the frequency coverage of the Australian MWA telescope, while providing higher resolution for a more detailed look at the cluster.
NCRA Centre Director Prof Yashwant Gupta said, “This is a great example of how archival data from the GMRT can be mined for interesting new finds and justifies the efforts and resources NCRA has put in to preserve every bit of interferometric data taken with the GMRT since its inception in 2002.”
The GMRT data is from 2008, taken with a modest bandwidth of 8 MHz using the old, legacy system of GMRT. “Today, with the upgraded GMRT, offering up to 200 MHz bandwidth in the same parts of the radio spectrum, we can do much better with observations of this kind,” said Prof Gupta.
“We’ve seen outbursts in the centres of galaxies before but this one is really, really massive,” said Professor Melanie Johnston-Hollitt from the Curtin University node of the International Centre for Radio Astronomy Research in Australia.
The explosion occurred in the Ophiuchus galaxy cluster, about 390 million light years from Earth. It was so powerful it punched a cavity in the cluster plasma -- the super-hot gas surrounding the black hole.
The blast was similar to the 1980 eruption of Mount St Helens, which ripped the top off the mountain, said lead author of the study Simona Giacintucci from the Naval Research Laboratory in the US.
“The difference is that you could fit 15 Milky Way galaxies in a row into the crater this eruption punched into the cluster’s hot gas,” she said.
The cavity in the cluster plasma had been seen previously with X-ray telescopes, Johnston-Hollitt said.
The researchers only realised what they had discovered when they looked at the Ophiuchus galaxy cluster with radio telescopes. “The radio data fit inside the X-rays like a hand in a glove,” said co-author Maxim Markevitch, from NASA’s Goddard Space Flight Centre.
“We’ve been given the tools to dig deeper with low frequency radio telescopes so we should be able to find more outbursts like this now,” Johnston-Hollitt said.
