Dr James Miller-Jones
Black holes, relativistic jets and our powerful Universe
Supermassive black holes change too slowly for us to observe, but their smaller cousins might provide some clues to their properties.
Dr James Miller-Jones is studying the powerful jets of plasma launched by low-mass black holes within the Milky Way, aiming to understand how they work. He hopes this will provide new insights into the workings of supermassive black holes in distant galaxies.
For James, who has been interested in astronomy since way back when, using giant radio telescopes and planning for the SKA pathfinders is all about discovery and solving the mysteries of the Universe.
“Every time I look at a set of telescope data, there is the possibility of finding something new and unique, something that no-one else has ever seen before. When I’m on the cusp of a new discovery like that, I can’t go to sleep until I’ve got the answer.”
Research Specialisation: Radio jets in X-ray binaries
The interview below was conducted in 2011
What are you working on now?
I’m working on a number of projects, all related to the goal of understanding jets in X-ray binary systems. These are double-star systems consisting of a compact object (a black hole or neutron star) in close orbit with a less-evolved, “normal” star. The strong gravity of the compact object causes gas to be transferred from the donor star to the compact object, and the high energies and strong magnetic fields close to the compact object can launch jets of energetic plasma travelling away from the star system at close to the speed of light.
This coupling between inflow of gas towards a black hole and the launching of powerful jets is seen throughout the visible Universe, from stellar-mass black holes in our own Milky Way Galaxy to the supermassive, billion-solar mass black holes at the centres of other galaxies. The removal of energy by the jets has an effect on how fast the black hole can grow, and the energy of the jets heats the surrounding gas, providing an important feedback effect on the evolution of galaxy clusters. However, the massive black holes at the centres of galaxies evolve very slowly, on timescales of hundreds of thousands of years, making them difficult to study. In the smaller stellar-mass black holes within our own galaxy, these processes are sped up such that changes occur on human timescales (months to years). So by using these stellar-mass systems as probes, we can try to understand how the inflow of gas is coupled to the launching of jets. This in turn has wider implications for their scaled-up cousins at the centres of galaxies, which are some of the most powerful objects in the Universe.
What got you into astronomy?
I’ve been fascinated by astronomy since I was a child. My high school had its own telescope, and we were occasionally allowed to use it during the winter months when it was dark early enough. I vividly remember the first time I saw the moon through the telescope and realised it was just another piece of rock moving through space. This was all happening at the same time as my high-school physics teacher was giving us an introduction to relativity and quantum theory. Thanks to this combination of new and amazing observational and theoretical concepts, I was hooked. However, I wasn’t planning career in astronomy at that stage, but I enjoyed Physics at school and went on to study it as an undergraduate (after narrowly escaping a career in medicine). Most of the course consisted of core subjects, but we could also choose a few options that we found most interesting. Following my own interests led me naturally to a PhD in astronomy, since when I’ve never looked back!
Why is your work important for ICRAR?
My work makes use of some of the new capabilities that ICRAR has been working hard to establish, showcasing some of the science that can be done with the new technology of e-VLBI (real-time radio astronomy) and the improved angular resolution that the ASKAP and Warkworth telescopes provide to the Australian Long Baseline Array. By demonstrating what can be done with a high angular resolution capability in the southern hemisphere, my work is contributing to the science case for including long baselines (up to 3000 km) in the SKA.
Why did you join ICRAR?
I was excited by the potential of ICRAR. As a rapidly-growing group with strong links to the SKA, and an impressive array of expertise in both scientific and technical aspects of radio astronomy, it seemed to have it all. My area of research falls right at the intersection of both the Variable Universe and the Very Long Baseline Interferometry projects within ICRAR, so it seemed like a perfect match.
Where were you before you came to work for ICRAR?
I came to ICRAR after a three-year stint working in the USA for the National Radio Astronomy Observatory (NRAO) as a Jansky Fellow, based in Charlottesville, Virginia. NRAO runs three major radio telescopes in the USA, and is one of the leading players in the construction of ALMA in Chile, the Atacama Large Millimetre Array, which will be the most powerful millimetre-wave telescope in the world. With a diameter of 110m, the Green Bank Telescope is the largest moveable land-based structure on the planet. The Expanded Very Large Array is currently the most sensitive radio telescope at centimetre-wavelengths (soon to be superseded by the SKA!), and the Very Long Baseline Array is a network of ten telescopes scattered across the USA, from Hawaii to the Virgin Islands. While at the NRAO, I used this suite of facilities to pursue my research into relativistic jets from X-ray binary systems.
What’s your favourite part of your work?
The potential for discovery. Every time I look at a set of telescope data, there is the possibility of finding something new and unique, something that no-one else has ever seen before. And while most of those discoveries are only very small pieces of a much bigger puzzle, you have a sense that the overall picture is gradually coming together, one piece at a time. And those very rare “eureka moments” that accompany a big new result make everything worthwhile; when I’m on the cusp of a new discovery like that, I can’t go to sleep until I’ve got the answer.
What do you think is the most exciting thing about astronomy today?
Being interested in black holes, I’m really excited by the new tests of strong gravity that will be enabled by the SKA. By making very accurate measurements of the arrival times of the regular bursts of radiation emitted by pulsars (rotating neutron stars), astronomers are attempting to detect for the first time the gravitational waves that Einstein predicted should be emitted when very massive objects move. Furthermore, the SKA hopes to discover a large fraction of all the pulsars in the galaxy. Some very small fraction will contain a black hole in orbit with the pulsar, and the motion of the pulsar (which acts as a very regular clock) in the strong gravitational field of the black hole will provide other stringent tests of general relativity, and allow us to learn more about the exotic objects we call black holes.
While it’s a little more outside my chosen field of study, I can’t help being fascinated by the biggest questions of all; where did the Universe come from and what is going to happen to it? Astronomers have recently discovered that the expansion of the Universe appears to be accelerating, and attribute this to a mysterious quantity called dark energy. I find the efforts to understand dark energy to be another of the most exciting areas of astronomy today, and again this is a field where the SKA can make a major contribution.