Black holes: the realm of extreme physics
Take a look at the universe with our Professor of Extragalactic Astronomy, Carole Mundell.
It's a privilege being able to make a living doing something you love.
“I have looked further into space than ever human being did before me,” wrote William Herschel in 1780. From his garden in New King Street, Bath, Herschel had scanned the night sky using a telescope he had built himself and saw Uranus. It was a discovery which effectively doubled the size of the then known Universe, and secured his adopted city a place in the history books.
Twenty-first century astronomy moves faster than in the days of the ‘gentlemen astronomers’. As ever more powerful telescopes come on line, discoveries are being made every day; yet to be successful in the field still requires Herschelian curiosity, ingenuity and a can do approach. Enter Bath’s stargazer-in-residence, Professor Carole Mundell.
Carole, Professor of Extragalactic Astronomy, joined the University of Bath as head of Astrophysics, and is now Head of our Department of Physics, while leading our Physics with Astrophysics undergraduate course and also building up her new research group.
Carole is animated as she discusses her research. “I’m particularly interested in black holes of all sizes and scales, their origin and influence on the environment around them, and ultimately how we can use them to probe broader laws of physics,” she explains.
The term ‘black hole’ is scientific short hand for a dense region of space inside which the pull of gravity is so strong that nothing can escape, not even light. Matter circulating near, but not inside the black hole, will heat up, shine brightly and may even be kicked back out into interstellar space if magnetic fields are there to drive the matter outwards, away from the hungry black hole.
Carole has spent her career studying black holes and their environments, winning prestigious fellowships and awards. “The physics of these systems are still poorly understood but we’ve found many examples using ground-based and space-based teloscopes,” she explained. “The most powerful kind are called gamma ray bursts and they challenge both our theories and technologies.”
Gamma ray bursts were discovered by accident in the 1960s, when miliarty satellites orbiting Earth mistook them for evidence of rogue states breaking the nuclear test ban treaty. Now confirmed as cosmic rather than terrestrial in origin, these bursts are compelling because they represent what Carole terms ‘the realm of extreme physics’.
“Ultimately the universe is a very good place to test the laws of physics because we have some of the highest energy processes and the greatest distances over which to test things,” she explains. “Because these bursts are associated with strong gravitation and magnetic fields, they’re in the kinds of places in the universe where we hope to discover and test new laws of physics.”
By analysing gamma ray bursts using telescopes around the world and in space, observational astrophysicists like Carole gain information about the physical processes that produced them. But their field is at a tipping point.
Currently around two bursts are recorded a week, but new facilities under development are set to revolutionise their work by surveying vast swathes of the sky in real time. Carole’s team are at the vanguard of this new kind of science but the possibility of receiving notification of up to a million new events every night is daunting. This ‘big data’ challenge is one which Carole predicts will require interdisciplinary innovation, bringing together astrophysicists, mathematicians, physicists, engineers and computer scientists.
Widening the path
“Astronomy for me was not a childhood hobby,” Carole admits, “but my parents were very supportive of my learning. My father, a biomedical scientist, encouraged my brother and me to do simple experiments such as growing salt crystals, testing for acids or alkalines, doing chromotography using blotting paper and ink. We were learning about the scientific method without realising it.”
Carole’s high-school teachers further encouraged her talent for physics. She puzzled over the deeper physics underlying basic high school physics. After a lesson on energy, she was concerned she was failing to understand something important. She asked her teacher ‘But what is energy?’ “He reassured me not to worry about it for my exam, but to think about going to university, where I might learn why this was such a difficult question to answer!” she laughs.
She duly won a place at Glasgow University to read Physics, but her first year Astronomy module wasn’t an instant hit. “Astronomy was a culture shock; it seemed a much more approximate subject than physics and there were no women lecturers in the astronomy group,” she says. “I was pretty sure I was going to drop the subject at the end of my first year, but then I saw Professor Dame Jocelyn Bell Burnell speak at the student physics society. I was captivated. The thrill of discovery and the real world of cutting-edge astrophysics research – suddenly, I could see this was a real choice for me.”
Carole is a strong advocate for diversity in science and is keen to inspire others in the way that Jocelyn Bell Burnell inspired her. “Physics has traditionally been male dominated, with the popular stereotype of a physics professor being a white man with a beard! People like Jocelyn cleared a tiny, narrow path for women like me to come through. We need to continue this so that physics is open to all, irrespective of gender and ethnicity.”
In 2016, ahead of hundreds of candidates, Carole was named Woman of the Year at the FDM Everywoman in Technology Awards, which celebrate outstanding achievement in fields traditionally dominated by men.
“Winning was completely unexpected. The Everywoman team kept the names of all the award winners secret until the moment they were announced on the night. It was a great honour to be named Woman of the Year amongst so many remarkable women leaders in their fields. It is fantastic that the impact of fundamental science done by me and my team has been recognised but also that my contribution to my wider community is seen as important,” she says. “These kinds of awards are vital to break down the traditional stereotypes and one hopes that, some day, the fields of science and technology will have parity so that there will be no need for them, but we are not there yet.”
Carole welcomed the increased media coverage of space events such as Major Tim Peake’s time at the International Space Station. “Astrophysics and space catch the human imagination and attract the brightest pupils to study physical sciences and engineering,” she says. But it is more than beautiful images. “There are days when you need to work on your error analysis, or figure out why a technique or piece of technology isn’t working. You have to be patient, dogged and stubborn.”
Carole spoke to audiences at New Scientist Live about her research. If you were lucky enough to catch her either at this event or another in the future, you’ll be in for a whirlwind experience as she whizzes through her research, from a brief history of cosmic endeavour from Copernicus to Einstein, to what a gravitational wave sounds like, to why the black hole portrayed in Hollywood blockbuster Interstellar should have failed its screen test.
Typically, her audiences are mesmerised, and bombard her with questions. Why is our galaxy flat? What would happen if you fell into a black hole? If the universe is expanding, where is it expanding into?
“It is a privilege being able to make a living doing something you love,” Carole admits. And it’s clear that her enthusiasm rubs off on her audiences as she speaks – some of whom might become candidates for studying Astrophysics here at the University in years to come.
When William Herschel built his telescope it was unthinkable that he would discover a whole new planet through it. Whatever discovery the world is on the verge of next, there’s a good chance that Carole, her research group, and students at Bath will be at the forefront.
Extract from 'Extra Galactic', an article by Rachel Skerry in Bath alumni magazine BA2