Dead satellite shows new horizon for X-ray astronomy
Tokyo: A dead Japanese X-ray satellite has offered astronomers, including an Indian researcher, the capability to measure detailed dynamics of extremely hot gas in a distant cluster of galaxies — allowing them to explore how galaxies form and evolve over time.
“Hitomi has revealed the tremendous scientific potential of next generation X-ray astronomy. This is only the first peek into a universe of discoveries. For instance, Hitomi was supposed to observe all kinds of growing black holes in order to learn how these ultra-dense objects grow and evolve,” said Poshak Gandhi from the University of Southampton.
However, the satellite suffered a fatal anomaly in March just one month after its launch. But before its untimely demise, its X-ray spectrometre was able to peer into the Perseus cluster of galaxies — a collection of thousands of galaxies bound together by gravity located about 240 million light-years away.
Measurements of unprecedented data revealed that superheated gas at the cluster’s heart flows much more calmly than expected, given the amount of astrophysical action in the region.
The astronomers discovered that the hot gas was moving in the cluster at 164 km per second – enormous by human standards but surprisingly modest on cosmic scales.
The results were recently published in the journal Nature.
The study also indicated that turbulence is responsible for just four per cent of the energy stored in the gas as heat.
“Of course we had a programme planned to look at more clusters, and we would have carried on for the next few years had it only lived,” said Andrew Fabian from the University of Cambridge and a member of the Hitomi team.
“It feels like the door has been briefly opened, showing us a new and exciting landscape – and it’s been slammed in our face again,” he added.
Led by the Japan Aerospace Exploration Agency (JAXA), Hitomi was launched on February 17 and made the Perseus observations on February 25 and March 4, weeks before suffering a mission-ending spacecraft anomaly on March 26.
The satellite’s revolutionary Soft X-ray Spectrometre (SXS) provided 30 times the detail of the best previous observation. Hitomi’s SXS could measure the turbulence in the cluster to a precision of 10 km/second, whereas previous observations could only constrain the speed to be lower than 500 km/second.