New X-ray telescope sheds light on black holes

A jet of energy particles shines bright x-rays onto the gas disc circling a black hole

NASA announced new findings from the Nuclear Spectroscopic Telescope Array (NuSTAR), the newest telescope observing black holes, on Feb. 26. For the first time, astrophysicists have accurately measured the “spin” of a black hole. This spin is thought to indirectly generate x-rays which light up the massive cosmic clouds circling the black hole. The researchers expect this will lead to a new understanding of how these giants evolve.

These are NuSTAR’s first significant findings after its launch in June of last year.  It now works in conjunction with another telescope, the European Space Agency’s XMM-Newton, to measure a wide spectrum of x-rays generated by a “jet” of energy firing from black holes. According to Fiona Harrison, NuSTAR’s principal investigator, this “jet” is powered by the black hole’s spin and acts “like a flashlight” reflecting x-ray energy off the accretion disc – a massive plane of gas, iron, and cosmic material that circles the black hole. This is how researchers infer the existence of the invisible – but incredibly dense – body at the centre. The greater the energy, the faster the black hole’s spin and the more massive it is believed to be.

But the x-rays emitted can often become distorted by surrounding gas clouds. The ultra sensitive NuSTAR can pinpoint the origin of these x-rays from millions of light years away and rule out any dust cloud interference.

Astronomer Guido Risalti said this point of origin is “smaller than a single pixel,” referencing a large picture of galaxy NGC 1365, the source of these findings. Yet the energy produced in this tiny speck at any given time is equivalent to “a billion suns shining for a billion years,” Harrison added.

Though smaller black holes exist throughout galaxies, the behemoths that form at the centre may pose challenges to Einstein’s general theory of relativity. According to the new data, the one at the centre of galaxy NGC 1365 is approaching the maximum spin rate allowed by the theory.

Next, NuSTAR will continue to collect similar data from other galaxies. These comparisons will give astrophysicists a window into the universe’s most extreme environments  – where gravity is strong enough to warp space and time.

Front page photo courtesy of NASA

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