What is a Numerical Astrophysicist?

This month I had the chance to speak to someone in Italy!  So far I have interviewed people in Ireland, England and America.  Franco was kind enough to offer to speak with me via a Twitter campaign a few months back now.  Thanks so much!

Tell us about yourself Franco?

My name is Franco Vazza, I am a numerical astrophysicist at the University of Bologna (Italy) and I lead a small group of young scientists, funded by the EU, named MAGCOW: the MAGnetised COsmic Web .  I was born in 1979 and spent several years of my career at the University of Hamburg (Germany) and moved back to Italy a couple of years ago, together with my wife (an astronomer too) and our son.

So here are a few details on what I do, hoping this helps to figure out what a numerical astrophysicist does.

How long have you been an numerical /theoretical physicist, please tell us about the field you specialise in?

I would say I am a more or less a full-time numerical astrophysicist since the start of my PhD, in 2006.  I was lucky to find a project the perfectly suited my interest: a study of shocks and turbulence of gas in the largest structures of the Universe, clusters of galaxies. I did that at the Radio Astronomy Institute in Bologna (a place where most of the people are not doing simulations but observing with radio telescopes instead), which gave me a broader idea of what simulations should be useful for.  It helped me understand how complex astrophysical processes may work and have originated the things we observe in reality.

Any observation, especially probing what happens beyond our Solar System, can only show a time snapshot of a long sequence of events that may take up to billion years (for example, to form a galaxy or a cluster of galaxies). We desperately need the most detailed observations as possible to have a clear picture of what is out there, after this we would be hopeless in understanding them if it wasn’t for the great body of physical laws and theories that many generations of scientists have worked out.

A numerical astrophysicist tries to use these laws to simulate the past of cosmic structures with a computer, and hopes that the simulated models are reasonably similar to real observations. If many observations can be matched by the same simulation, than it becomes increasingly more certain that the set of physical laws we taught the computer are really at work out there. If this is not the case, in the continuous process of revision of these laws or theories, we learn something about how the Universe work.

Examples to Look for:

Here the example of a couple of simulations:

This one shows how a cluster of galaxies is supposed to have emerged out of a very hot and uniform gas (soon after the Big Bang)

This one shows instead how we think the “cosmic web” of galaxies is structured over billions and billions of lightyears, as rendered by a numerical simulations.

Why did you pick this particular field of study?

Using numerical simulations and “super computers” (which are big clusters of hundreds of thousands of computing processors, located in big rooms and working 24/7) requires a great level of precision and exactness.   Computer programs are easily “broken” if just a few characters are wrongly written in documents of hundreds of thousands of lines, which are the instructions we give such supercomputers. For example, wrongly dividing by 2 (instead of multiplying by 2) somewhere in these codes may lead you to very, very wrong predictions about the Universe observed by telescopes.

So, in general this is a kind of research best suited for people which are meticulous and very skilled in mathematics…but I’m afraid I do not have enough of these qualities. Indeed at the begin of my studies I decided that doing numerics wasn’t my thing!

However, I’ve been sucked into numerics by a scientific question I wished to solve: I was curious to know if there was turbulence (like swirls or vortices) in the largest patches of gas we know exist in the Universe: the intergalactic space in between galaxies, within so-called clusters of galaxies.  They can span millions of lightyears across, and emit copious amounts of energy in X-ray radiation, which we observe through X-rays. However, knowing how fast these giant clouds of gas are moving has been impossible for decades, and basically none knew whether there could be large plasma  tornadoes in this environment, or not.

It turns out that turbulence is such a complex phenomenon, that there is little one can do with “simple” pen and paper calculations, so one needs to resort to larger and larger computer simulations to be able to visualize how many gas clouds and mix and self-disrupt, inducing a whole hierarchy of vortices. So this is what I first worked on during my master thesis, and have also kept doing ever since, using larger and larger simulations. This one (hell.png) is one of the first beautiful simulated images of gas turbulence across 50 millions light years I produced around 2010,  for on of my first scientific work on this subject.  It is the result of many tens of thousands of hours of computation, and it gives us a visual ideal of how complex should be the flow of gas in between galaxies, on scales of millions of  lightyears. While most of these details should remain invisible probably forever in real systems, future X-ray telescopes (like for example the Athena X-ray satellite https://www.the-athena-x-ray-observatory.eu) should be able to give us at least a sense of the gas circulation in the innermost parts of galaxy clusters.

What is a Numerical Astrophysicist?

What did you want to be when you were younger?

When I was really young, I wanted to be an archeologist (Indiana Jones was a big thing in those years!). Later, a philosopher, and more later, an physicist. I would say being an astrophysicist combines many aspects of the above professions: we are actually studying the most ancient things in the Universe, and sometime wondering about their meaning in relation to our life, and we are using physics as a language to describe all this…so indeed becoming an astrophysicist was a good catch for me, as a little bit of all the above is combined.

Why would you suggest this as a job for me?

I wouldn’t dare to suggest anything in particular!

The only secret I know, is to try succeeding in a job that you actually do not perceive as a real job…so you would rarely feel any stress from it.

Science in general is good way to obtain this, because many of the questions continuously arise along the way.  So there is always a challenge to face, and this is a formidable trigger for curiosity and amusement. Any job which can keep these two things alive, would be a good choice in my opinion.

What qualifications did you need?  Where did you study?

You definitely need a Master and than a PhD in Astronomy or Astrophysics or Physics for this.

I graduated in Astronomy at the University of Padova (Italy) and took the PhD at the University of Bologna (Italy), the most ancient in the world, in 2009. Additionally, most professional astronomers would spend (sometime as a choice, sometime as a need) several years abroad after the PhD, in a “Post-Doctoral” fellowship, increasing their skills and knowledge.

Who would be your hero?  Who would you be excited to meet in your field?

Since I have recently re-started playing tennis, my hero of the moment is tennis star Roger Federer 😛

But speaking of science, it would probably someone less of a superstar, like famous physicists from the former Soviet Union, like Lev Landau or Yakov Zeldovich.  Great minds that had to rely on only very little or nothing on numerical computations, and could still solve with the power of their mind great mysteries.  They can predict real phenomena that people could observe only decades after. Unluckily, we are well separated in time, so having a dinner together won’t be possible anymore; however at conferences sometimes I meet senior scientists that actually met some of the two during their early studies, so I am often bugging them with all curiosities I have about my heroes.

What has been the “best day” at your job?

At least in my case, there is rarely a “wow” moment, because I don’t work with observations and I cannot “discover” things by being the first one to look at it as telescope image.  However my fellow observers are often lucky to have this in their routine.

For me, the most of excitement comes when I think I’ve found a good explanation for some phenomenon, or conversely when I think I’ve found a mystery or problem in the theory, that went unnoticed before.

After this first spark of joy, there is however some time to wait before being sure of my thought, which involves reading a lot of articles, speaking with other people and so on. So the emotion is somehow “diluted” over many days (or eventually is totally dissolved by the discovery my idea was wrong, as can always happen).  But in general, a good day is a day in which I’m confident I am thinking of something new, which can potentially have a significant impact on astronomy. Simulations are good for this, because they offer you a visual support for your intuitions, sometimes!

So when my simulations support something I’ve thought about for a while, that’s a very good day!

How did you end up working at Unibo?

It’s where I took the PhD and where there was a job opportunity, almost ten years later, to have myself and my wife (an astronomer too) hired in the same place, something quite rare! Finding a good position in the same city at the same time is a big challenge for many couples of astronomers, but in our case it was very important as we also have a 5 years old child. Actually, this enterprise would have been close to impossible, but we were lucky to win both at the same time an important European grant, which enabled our University to directly hire us.

I actually would have stayed other 10 years in Germany if possible, because my working conditions at the Observatory of Hamburg were really fantastic…but it was a kind of “now or never” choice. Anyways, I am very happy of our new (probably permanent) location, and even if in Italy one has to struggle to find funding for his research (as in most places), the struggle for science is definitely worth it.

What is coming up next for you?

At least for the next few years, I will keep focusing on the mysteries of “cosmic magnetism” with my groups of researchers; this involves following many different kind of questions, from the observational ones (“how could we possibly observe this manifestation of magnetism with the available telescopes”?) to the more speculative ones (“how could such intense magnetic field have emerged in this class of objects”)?

This project has been funded by the European Union in 2017 and will last 5 years, and gave me the resources to recruit a group of enthusiastic young researchers (at present, 6 other people beside me, 3 females and 3 males, all from different countries).

What keeps our project together is the usage of numerical simulations as a tool to investigate, both, theoretical scenarios for the origin of cosmic magnetic fields and to interpret the complex observations that radio telescopes are producing or will be producing in the near future.

Radio observations give consistent evidence of spectacular structures tracing magnetic fields (millions of times smaller than the ones we can experience on Earth, for example in the small magnets on our fridges) as large as 6 millions light years, which are non trivial to explain.

A famous example is the large linear structure in one galaxy cluster, now called “the Toothbrush” radio relic: here is the most spectacular image of this, captured by one MAGCOW researcher, Kamlesh Rajpurohit (just before she joined us.  Check the image below.

We are struggling to understand what can cause the odd shapes radio observations detected along the axis of the toothbrush, and at the same time we are wondering what caused this very extended and volume-filling magnetic field. Was it produced soon after the Big Bang, by the same processes that formed the first chemical elements of our Universe, or the “seeds” for that magnetic field were produced only much later, during the explosion of supernovae? The jury is still out about this, and our simulations are being used to predict how the two scenarios would look like.

We think a big breakthrough will be possible thanks to the deployment of the Square Kilometer Array (SKA, https://www.skatelescope.org) which is the biggest astronomical challenge in building a instrument ever attempted. It should become operational in a decade from now, but meanwhile our simulations can suggest what it should be able to see, and what are the best strategies to detect the very elusive weak magnetic fields in between galaxies, also joining forces with X-ray telescopes (like Athena).

A recent simulation we did for this is visible here  https://youtu.be/66WbAZqzu2c

Thanks so much for your interview Franco!   I hope you’re enjoying my interviews with these amazing people?  Let me know if there is anyone you would like to hear from and I will do my best to reach someone for you.

Related News

Show Buttons
Hide Buttons