Professor Anna Watts (1992)

Professor Anna Watts matriculated at Merton in 1992 to read Physics. Following her degree, she joined the Civil Service Science and Engineering Fast Stream for five years. Though she enjoyed her time at the Ministry of Defence, Anna found that she missed research science. Contemplating a PhD, she came back to Merton to speak to her former tutor, Professor James Binney, for advice. Professor Binney mentioned research being done by Professor Nils Andersson in the General Relativity group at the University of Southampton and, as Anna says, “the rest was history!”

It was in 2000 that Professor Watts joined the University of Southampton, where she completed a PhD in Gravitational Wave Astrophysics. Following this, in 2004, Anna moved to Washington, DC to take up a National Research Council Postdoctoral Fellowship at NASA's Goddard Space Flight Centre. Anna went on to the Max Planck Institute for Astrophysics in Munich, Germany, where she continued her research into neutron stars. She is currently Professor of Astrophysics at the Anton Pannekoek Institute for Astronomy, University of Amsterdam, where she has worked since 2008.

Anna’s research is fascinating. Looking at the stars, neutron stars that is, she examines the dense nuclear matter in their cores and studies the violent dynamical events that they undergo, such as magnetic and thermonuclear explosions and starquakes. Professor Watts is part of the team working on NASA's Neutron Star Interior Composition Explorer (NICER), a telescope on the International Space Station that was launched by a SpaceX Falcon 9 rocket in 2017. NICER makes extremely detailed X-ray measurements of neutron stars, as seen in this captivating video.

Besides working with the NICER team, Professor Watts is involved in developing the science case for the next generation of large-area X-ray telescopes such as the proposed Chinese-European Enhanced X-ray Timing and Polarimetry (eXTP) mission and the NASA probe mission concept STROBE-X. She is a Scientific Editor for Monthly Notices of the Royal Astronomical Society, and was recently awarded a €2 million Consolidator Grant from the European Research Council for her proposal AEONS: Advancing the Equation of State of Neutron Stars.

Though there is a growing number of women working in astrophysics, the gender imbalance in this field nevertheless remains one of the largest in academia. This makes it even more extraordinary that Professor Watts has reached such a senior level and accomplished so much. She is at the forefront of new and exciting technologies, researching the unknown, and opening up a new chapter in our understanding of neutron stars. It is little wonder that she is one of Merton’s prominent Physics alumni and an inspiration to women throughout the world.

Merton & Me

Thinking of the first day you walked through the Merton Lodge arch as a student, what was your first impression?

That I was nervous, excited, lucky, and looking forward to seeing all of the people I'd met at interview again!

Do you have a particular memory that stands out from your time at Merton?

Working late in the library on Mob Quad just before Finals and finally feeling all of the pieces of physics that we had studied start to come together and make sense.

Tell us something about yourself that we would not know.

For the last few years I've been a member of the 'Brexit Panel' for a Dutch radio programme.
What tips would you give your younger self to prepare for the career you’ve achieved?

Pay more attention in your statistics lectures, because it turns out you're going to use it and enjoy it! And don't let anyone stop you asking those stupid questions, because they will turn up very interesting answers.

Describe Merton in three words.

Cosy. Beautiful. Eclectic.

An interview with Anna Watts

Can you tell us a bit about your research? And perhaps offer a short explanation of what neutron stars are.

Neutron stars are objects of incredibly high density, and quite small, maybe 15-30 kilometres across. They are essentially dead stars, consisting of extremely tightly packed sub-atomic particles, and are created when a massive star exploded in a supernova. Pulsars are rapidly spinning neutron stars that sweep out beams of energy, and that’s what we can observe and measure. My research is aimed at taking those measurements to work out what neutron stars are made of and also investigating explosions on neutron stars. I work on theoretical modelling using X-ray telescope data.

Did you always know you wanted to be an astrophysicist? And can you tell us the route you took to reach where you are today?

No, I hadn’t wanted to be an astrophysicist from childhood. I didn’t even particularly want to do Physics A-level, but my school felt that Physics went better with Chemistry and Maths than History did. Anyway, in the science area at school I saw a poster on the wall for the European Space School, which attracted my attention. So I went to Brunel for a two-week summer course on space. (The course still exists, but it’s now three weeks long and run from Leicester.) Helen Sharman, the first British astronaut, was one of the lecturers; she was brilliant and so inspiring. It really made me think that astrophysics was something I wanted to study. But the advice I was given there was that it was better to do a general degree in physics first.

I came from my school in Bradford to Merton to study physics, and I took astrophysics modules where I could. I really enjoyed the physics, but at that point I didn’t want to stay in academia.

So I thought I would try something else. I left university and went into the science fast stream in the Civil Service for five years, but after that time I realised I was missing doing research, so decided to apply for a PhD. I came back to Merton to talk to Professor James Binney, who had been my tutor. He gave me some ideas as to where I should apply. In particular, he mentioned an astrophysicist at the University of Southampton. I went to visit, liked the guy, loved the research topics, and ended up doing my PhD there. My thesis was called ‘The dynamics of differentially rotating neutron stars’, and it involved trying to compute gravitational wave signals from newly formed neutron stars. It was very theoretical and I loved it.

The Civil Service had generously given me three years of unpaid leave, but I decided not to go back after my doctorate. Instead, I got a postdoctoral fellowship at NASA’s Goddard Space Flight Center in Washington, DC. There, I was working within a more observational department, including X-ray telescopes, and that’s when I first got my hands on some real data. It was clear that I needed to see data to test my models.

From there I went to Germany, on another postdoctoral fellowship, to the Max Planck Institute for Astrophysics in Munich. Here again I was working with the same mixed group of X-ray and gravitational wave scientists.

Then, in 2008, I got the chance to come to the University of Amsterdam, and fairly soon afterwards got a faculty position, and I’ve never left. Here at the Anton Pannekoek Institute for Astronomy, we have one of the lowest-lying observatories in the world for an optical telescope – the building is below sea level. But my research is concerned with X-ray observations, and those have to be done from telescopes in space.

NICER on the International Space Station © NASA

You work on NASA’s NICER mission. Can you explain what this is?

NICER, the neutron star interior composition explorer, is a telescope on the International Space Station. It was launched in 2017 and takes very detailed X-ray measurements of neutron stars, so we can determine their mass and radius and thus work out how big they are and, we hope, eventually find out what they are made of.

The technique that NICER uses is one that will also be exploited by the next generation of telescopes, to be launched later this decade. It was because of my team’s work on the technique for these future telescopes that we were invited to join the NICER collaboration. This means that we get the benefits of its data about a year before it is formally made available to others. We got some exciting first results and published them at the end of last year.

What has been the most exciting moment in your career so far?

In fact, it was the work with NICER. We were able to use the technique that we had developed to get a simultaneous measurement of mass and radius for a particular neutron star, with about 10% uncertainties. That was very exciting – to discover that our theoretical technique actually worked in practice. We determined that this neutron star was about 16 miles (26km) across and about 1.4 times the mass of the sun.

A by-product of this was to find out where on the neutron star the X-rays come from. The magnetic field of the neutron star funnels particles towards the magnetic poles, heating them up until they emit X-rays; as the neutron star – or pulsar – spins around, the hot poles move in and out of our line of sight, and we see this as X-ray pulses. Textbook theory was that the magnetic poles would appear as two spots on opposite hemispheres of the neutron star, but the measurements we observed showed them both on the same hemisphere, with one of the hot regions being a long thin arc rather than a spot.

This started a whole line of research by people who work on magnetic fields on neutron stars. We tell them where the spots are, and they can feed the information into their theories. So we are working with pulsar theorists as a result of our findings. We are now analysing a couple of other bright neutron stars that we think will yield even better results. All these neutron stars are several hundred light years away.

This work, first in developing the technique for the telescope and then interpreting the measurements, has been absolutely brilliant. We have got our technique through to completion and are learning more about neutron stars, which is the whole aim.

Any other exciting moments?

I was thrilled at discovering star quakes on neutron stars. While I was at NASA, we were observing a group of neutron stars with strong magnetic fields. They emit regular bursts of X-rays and gamma rays, and about every ten years or so there is such a massive eruption that it affects Earth’s ionosphere.

At the end of 2004, there was a very powerful event lasting several hundred seconds. We saw very high frequency ringing, at a similar pitch to a musical instrument. We think that we were seeing that big burst coming from a quake on a neutron star, which set the whole star vibrating.

We discovered this phenomenon in a couple of neutron stars. We saw them using both a dedicated X-ray telescope and also using a solar X-ray telescope that just happened to be pointing in the right direction at the time (solar telescopes wouldn’t normally receive data from neutron stars!). We were able to use the data from the solar telescope as well and confirm our discovery.

What would you say has been the greatest discovery in astrophysics in recent years?

Definitely, the biggest change in astrophysics in recent times has been the direct detection of gravitational waves in 2016. Scientists are now using them to study the interior of neutron stars. Having left the field of gravitational waves, I am now working closely with gravitational wave scientists again.

Image removed.
Notional magnetic field geometry of a pulsar derived from NICER X-ray measurements © NASA

What are the greatest unknowns in our knowledge of the universe? What are the most challenging questions to be answered?

It’s got to be dark matter and dark energy. But that’s not for me to work on! We still don’t know what neutron stars are made of – that will take the next generation of telescopes – and that is my job.

Would you like to go to Mars?

Yes! If I was eligible to go (which I’m not), I would go in a heartbeat. It would be fascinating.

Is astrophysics a hobby as well as a career for you?

Yes, it really is, in the sense that I find myself thinking about it all the time. But I do try and switch off – by doing a lot of sport. And I have two young kids, which helps.

Do you feel that you are in a minority, as a woman in astrophysics?

Yes, I am in a minority, and it does make a difference. For instance, here in Amsterdam we are part of a collaboration with China, on the Chinese-European Enhanced X-Ray Timing and Polarimetry mission. The team has a great many senior women, and the atmosphere is very different to previous collaborations I’ve been part of – it’s a completely different way of working. It’s important to have a good mix; it makes me sad that there are not more women and minority groups in my subject.

I do find myself breaking barriers. For example, I was the first female faculty member to have children at my institute, which meant that they had to make some changes. I’m also only the second female full professor in my institute. You might be surprised to know that the percentage of women professors is far lower in the Netherlands than in the UK.

What do you remember most about your time at Merton?

It was such a beautiful, historical place to be. Sitting in the Merton Library, being part of that history, was something special. Plus the privilege of being able to follow intellectual leads and ask questions, no matter how random, and know that my tutors would take the time to answer them. That was also priceless.

Finally, do you have any advice you would give to anyone who is interested in astrophysics as a career?

Find something you enjoy. Look for opportunities down the line – missions that are about to launch, rather than what’s going on at the moment. There are a lot of big collaborations, so it’s possible to find something that interests you. And keep up to date. Also, be very sceptical. Many discoveries have been made by people looking back through existing research and finding errors. You need tenacity and persistence to figure out what is really happening.