Combining observations from NASA’s Rossi X-ray Timing Explorer (RXTE) satellite and the National Science Foundation’s (NSF) Very Long Baseline Array (VLBA) radio telescope, principal investigator Dr James Miller-Jones, of The International Centre for Radio Astronomy Research (ICRAR), led a team of radio astronomers from around the world to make the discovery.
Dr Miller-Jones said identifying the moment when the ‘bullets’ of gas were launched would assist radio astronomers to better understand the physics of how and why black holes launch fast-moving flows of material outwards, which, in turn, could help to reveal more about similar processes occurring around super-sized black holes at the centres of galaxies.
“The research focuses on star systems called X-ray binaries. These are double-star systems in which a normal star is in a very close orbit with a black hole,” Dr Miller-Jones said.
“Due to their proximity, gas from the normal star is pulled in towards the black hole by its enormous gravitational field. Some of the gas that is spiralling inwards can be flung outwards in narrow beams of ionized gas that we call jets, probably with the help of very strong magnetic fields.
“This same process is seen in many different types of systems throughout the universe, from forming young stars to feeding black holes, both in binary systems and at the centres of galaxies, and also in the hyper-energetic explosions known as gamma-ray bursts.”
Dr Miller-Jones added that X-ray binaries provided ideal laboratories to study the process, as their jets form and evolve over just a few days, as compared to the potentially thousands of years taken for the same process to be completed around the black holes at the centres of galaxies.
“The jets are launched at speeds approaching that of light in an outburst producing about as much energy in an hour as the Sun emits in five years. We have been studying these jets to try to understand how they form and the impact they have on their surroundings.”
Dr Miller-Jones said the study had demonstrated a new way to make progress in understanding how jets were launched from close to a black hole.
“By making very high resolution observations with radio telescopes as a black hole starts ‘feeding’, we can track the motions of the jets, work backwards to find out when they were launched, and then use X-ray telescopes to determine what was happening at this time to the material falling inwards that could have caused the launching of the jets,” he said.
“We think that the same physics should apply to all black holes that are gobbling up matter from more normal stars, so the next step would be to see if the same sequence of events is seen in other, similar systems. If so, it would demonstrate that the process is universal.”
Dr Miller-Jones said if further studies revealed the process to be universal, it would bring scientists a step closer to understanding how the jets from the massive black holes at the centres of galaxies form and the impact they have on their galactic environments, even possibly affecting the evolution of the host galaxies.
Before beginning his work at ICRAR, Dr Miller-Jones was a Jansky Fellow at the National Radio Astronomy Observatory (NRAO), USA. Prior to this, he worked as a postdoctoral researcher, specialising in X-ray binary systems and transients at the Astronomical Institute at the University of Amsterdam.
Dr Miller-Jones has spent the past few years using the world’s premier radio telescopes to study jet-producing X-ray binary systems. He received his doctorate from Oxford University, UK, where he was a member of St. John’s College.
ICRAR is a joint venture between Curtin University and The University of Western Australia, in close collaboration with US, Indian and New Zealand partners.
For more information, including an animation of how scientists think the process occurs, you can visit the NASA website, at:http://www.nasa.gov/topics/universe/features/rxte-bullets.html
Dr James Miller-Jones, Research Fellow, ICRAR – Curtin University
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Andrea Barnard, Public Relations, Curtin University
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