2 March 2017
Artist impression illustrating a supermassive black hole with X-ray emission emanating from its inner region (pink) and ultrafast winds streaming from the surrounding disk (purple).
For the first time, astronomers have carried out a detailed observation of ultra-fast winds caused by black holes – which revealed that the winds can rapidly fluctuate from cool to extremely hot.
Supermassive black holes, which live in the centre of large galaxies and are millions to billions of times more massive than the Sun, devour the gas and debris surrounding them by sucking it in with their gravitational pull.
As a result of this frenzied consumption, the black holes then emit ultra-fast streams of gas – or ‘winds’ – which blast through their galaxy at nearly a quarter of the speed of light.
In this new research, an international team of scientists, including STFC funded researchers from the UK, have been able to closely observe winds from a nearby supermassive black hole for 17 consecutive days.
“We often only have one observation of a particular object, then several months or even years later we get to observe it again and see if there’s been a change,” says Dr Michael Parker of the Institute of Astronomy at the University of Cambridge, lead author of the paper published this week.
“Thanks to this long observation campaign, we observed changes in the winds on a timescale of less than an hour for the first time.”
This research has revealed the extremely variable nature of the winds, which heat up and cool down in the space of just a few hours.
Using ESA’s XMM-Newton and NASA’s NuStar telescopes the researchers studied the X-rays emitted from the edge of the black hole, which were altered by the winds as they travelled to Earth. By examining the changes in the rays when they reached Earth, astronomers learned more about the components of the wind.
The team noticed that parts of the X-rays were disappearing then reappearing, suggesting they were being heated to extremely high temperatures, millions of degrees Celsius, while passing through the winds.
The findings also show that these winds can transform their surroundings by disrupting the star formation in the host galaxy.
Dr Parker said: “Black hole winds are one of the mechanisms for feedback, where the energy coming out from the black hole regulates the growth of the host galaxy. Understanding these winds is therefore crucial to understanding how galaxies, including our own, grow."
STFC funds a number of international research projects which look into the nature of black holes, including gravitational wave research, which has recently revealed how the energy from colliding black holes can send ripples through space-time.
Further information on the project can be seen here.
Further information can also be found here.
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The paper is titled "The response of relativistic outflowing gas to the inner accretion disk of a black hole." The work was funded by the European Research Council, the European Union Seventh Framework Programme, the Science and Technology Facilities Council of the United Kingdom, the European Space Agency, and NASA.
NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. JPL is managed by Caltech for NASA.