Category: astrophysics

Addressing Early Career Astronomers

Every once in a while, I join events aimed at Early Career Researchers to talk about possible career paths, some personal experience in job hopping and to hopefully give some useful advice for ECRs when they’re on cross-roads in their professional life path. I like these events and find them to be very helpful for bouncing thoughts and raising awareness for aspects of career decisions that are not always on top of mind. For sure, there were things that I would have hoped to realize earlier in life. If you’re in need of somebody to exchange thoughts on such matters, feel free to contact me on LinkedIn or by email.

It’s important to have a bunch of people at such events, who all bring their own perspectives, experiences and personalities. A good choice for your own career depends on countless factors, and there really is no golden recipe for a successful, happy progression of your professional life. That said, there are some general things you might want to consider, and I wish events like the ones I sometimes attend would have been present 15 years ago, to teach my past me.

The event I attended yesterday was extra special. The yearly Dutch Astronomers Conference (also known under its Dutch name of Nederlandse Astronomen Conferentie, NAC) had an ECR event. For me, it was 14 years ago that I attended my last NAC. I had great memories of the meetings, packed with interesting science, but also a lot of fun social events in a great community. It was incredibly fun to meet old friends again. Obviously, I knew basically nobody of the younger generation, but I was surprised to see how many people I did still recognize. It felt like a reunion, or even like coming home after a long absence.

It was extra amazing that my master’s thesis advisor, and the astronomer who has been my great example ever since studying in Utrecht, was at the meeting, and attended my talk, too. As a scientist, teacher, mentor and astronomy popularizer, I do not know of a better example. Henny, thank you for catching up, and for being there yesterday and those numerous times before. It means the world to me. And indeed: if anybody would have inspired me to stay in astronomy, it would have been you.

The numerous valuable encounters made yesterday great. I hope that I added some value to the younger audience, who are facing some tough yet important decision on how to shape their future lives. In case it might useful to anybody, here are my slides for the event:

Academia and Industry – Moving back and forth? Download

Vanna, thanks for organizing these valuable events and keep up the good work with the NOVA-SKIES mentoring program! Stefania, thanks for the laughs and the ride home! Congrats and thanks for the fun, Steven. Lex: my memories (of 23 years ago!!) are fantastic too. They shaped my early astronomy life and they will last a lifetime, I’m sure. Scott, we need to keep the picture tradition alive, so in decades we can study some evolutionary patterns! Ilse, three events in a timeframe of just a couple of hours is impressive; good luck in your new role! And also to all the others I caught up with yesterday: thanks, I had a blast.

An old love: magnetic fields on the Sun

Dutch Open Telescope on La Palma, credits: astronomie.nl and Rob Hammerschlag.

Late 2003 and early 2004 I was a third year BSc student. I was lucky enough to be taken to La Palma by my professor Rob Rutten, presumably to use the Dutch Open Telescope, a fancy looking half alien with a 45 cm reflective telescope on top, that makes some awesome images (and movies!) of the solar atmosphere. It turned out to be cloudy for two weeks (on the mountaintop, lovely weather on the rest of beautiful island, not too bad….), so my “project” became more of a literature research and playing with some old data than an observational one.

A tiny part of the solar surface
A small part of the surface of the Sun. The lighter areas are the top of convective cells where hot gas boils up. Cooling gas flows down in the darker lanes in between. The bright white points are places where the magnetic field of the Sun is strong and sticks through the surface.

I started looking into “bright points” in “intergranular lanes”. The granules, see left, are the top of convection cells, pretty much the upper layer of the boiling sun. In the darker lanes in between the cooling gas falls back down to be heated and boiled up and again later. Inside these darker lanes you sometimes see very bright spots. These are places where bundles of magnetic field stick up through the surface. These contain some less gas, so you look deeper into the Sun where it is hotter, hence the brightness of these spots.

With different filters you can choose at which height in the solar atmosphere you look (more or less; I guess you understand I take few shortcuts in my explanation here…), so we can see how such regions look higher up and see what the gas and these magnetic bundles do. Looking at a bundle from the top isn’t necessarily very informative, but when you look near the limb of the sun, you are basically getting a side view of these things:

Images near the limb of the Sun in three different filters taken simulateously. On the left you see a side view of the image above (on another part of the Sun at another time, though). Moving to the right are filters that typically see a little bit higher up in the atmosphere (the so-called chromosphere). For the interested reader: the filters are G-band, Ca II H and H-alpha. Image taken from Rutten et al. 2012.

I spent about 3 months discussing with the solar physics group in Utrecht, which still existed back in the day, trying to figure out how these magnetic fluxtubes actually work. I wrote a (admittedly mediocre quality) Bachelor’s thesis about this work that ends with some speculations. I fondly remember how my supervisor did not like my magnetic field structure based interpretation and believed it was more related to effects of the temperature structure and corresponding effect on how the radiation travels through these bits of atmosphere.

I suddenly was drawn back to this topic two weeks ago, when I read the Dutch popular astronomy magazine Zenit. It was a special about Minnaert’s famous “Natuurkunde van ‘t vrije veld” and featured an an article by the designer of the DOT, Rob Hammerschlag, and talked about observations of the Sun, including these magnetic structures. I followed some links from the article and found myself browsing the professional solar physics literature from the past decade or so, on the look for the current verdict on these “straws” in the middle image above.

A detailed simulation of the solar surface and its magnetic field, by Chitta and Cameron from the MPS in Germany.

Obviously, the answer is slightly complicated and not as simple as mine (or my professor’s!) interpretation from 2004. While I was suggesting twisted magnetic field lines to be important, it turned out likely that the relevant phenomenon that is important in these straws are torsoidal waves through the tube (waves that you can make by grabbing it, and twisting like you twist the throttle of a motorcycle). Great fun to be taken back on a journey into the solar atmosphere, just by reading a simple popular article!

I regret quitting astrophysics

In 2013 I decided to quit my career in astrophysics, move back “home” and become a data scientist. The blog post I wrote about my decision was probably my best read publication as a professional astronomer and it was moving to read all the reactions from people who were struggling with similar decisions. I meant every word in that blog post and I still agree with most of what I said. Now, 7 years after the fact, it is time to confess: I deeply regret quitting.

This post is meant to give my point of view. Many people who left academia are very happy that they did. Here I present some arguments why one might not want to leave, which I hope will be of help for people facing decisions like these.

I miss being motivated. In the first few years after jumping ship many people asked me why I would ever wanted to not be a professional astronomer. I have always said that my day-to-day work wasn’t too different, except that what I did with data was about financial services or some other business I was in, rather than about galaxies and the Universe, but that the “core activities” of work were quite similar. That is kind of true. On an hour by hour basis, often I’m just writing (Python) code to figure things out or build a useful software product. The motivation to do what you do, though, is very very different. The duty cycle and technical depth of projects are short and shallow and the emphasis of projects is much more on getting working products than on understanding. I am doing quite well (in my own humble opinion), but it is hard to get satisfaction out of my current job.

I miss academic research. The seeds of astronomy were planted at very young age (8, if I remember correctly). The fascination for the wonders of the cosmos has changed somewhat in nature while growing up but hasn’t faded. Being at the forefront of figuring things out about the workings of the Universe is amazing, and unparalleled in any business setting. Having the freedom to pick up new techniques that may be useful for your research is something that happened to me only sporadically after the academic years. The freedom to learn and explore are valuable for creative and investigative minds and it doesn’t fit as well in most business settings that I have seen.

I miss working at academic institutions. The vibe of being at a large research institute, surrounded by people who are intrinsically motivated to do what they do was of great value to me. Having visitors over from around the globe with interesting, perhaps related work was a big motivator. That journal clubs, coffee discussions, lunch talks, colloquiums etc. are all “part of the job” is something that even most scientists don’t always seem to fully appreciate. Teaching, at the depth of university level classes, as a part of the job is greatly rewarding (I do teach nowadays!).

I miss passion and being proud of what I do. The internet says I have ”the sexiest job of the 21st century”, but I think my previous job was more enjoyable to brag about at birthday parties. I can do astro as a hobby, but that simply doesn’t give you enough time to do something substantial enough.

I don’t miss … Indeed, the academic career also had its downsides. There is strong competition and people typically experience quite some pressure to achieve. The culture wasn’t always very healthy and diversity and equality are in bad shape in academia. Success criteria of your projects and of you as a person are typically better motivated in business. The obligatory nomadic lifestyle that you are bound to have as an early career scientist were a very enjoyable and educational experience, but it can easily become a burden on your personal life. The drawbacks and benefits of any career path will balance out differently for everybody. If you get to such a point, don’t take the decision lightly.

The people who questioned my decision to become an extronomer were right. I was wrong. It seems too late to get back in. I think I have gained skills and experience that can be very valuable to the astronomical community, but I know that that is simply not what candidates for academic positions are selected on. On top of that, being geographically bound doesn’t help. At least I will try to stay close to the field and who knows what might once cross my path.

Hacking for a future data flood

Astronomy has always been a “big data science”. Astronomy is an observational science: we just have to wait, watch, see and interpret what happens somewhere on the sky. We can’t control it, we can’t plan it, we can just observe in any kind of radiation imaginable and hope that we understand enough of the physics that governs the celestial objects to make sense of it. In recent years, more and more tools that are so very common in the world of data science have also penetrated the field of astrophysics. Where observational astronomy has largely been a hypothesis driven field, data driven “serendipitous” discoveries have become more commonplace in the last decade, and in fact entire surveys and instruments are now designed to be mostly effective through statistics, rather than through technology (even though it is still stat of the art!).

In order to illustrate how astronomy is leading the revolutions in data streams, this infographic was used by the organizers of a hackathon I went to nearing the end of April:
Streams and volumes of data!

The Square Kilometer Array will be a gigantic radio telescope that is going to result in a humongous 160 TB/s rate of data coming out of antennas. This needs to be managed and analysed on the fly somehow. At ASTRON a hackathon was organized to bring together a few dozen people from academia and industry to work on projects that can prepare astronomers for the immense data rates they will face in just a few years.

As usual, and for the better, smaller working groups split up and started working on different projects. Very different projects, in fact. Here, I will focus on the one I have worked on, but by searching for the right hash tag on twitter, I’m sure you can find info on many more of them!

ZFOURGE

We jumped on two large public data sets on galaxies and AGN (Active Galactic Nuclei: galaxies with a supermassive black hole in the center that is actively growing). One of them was a very large data set with millions of galaxies, but not very many properties of every galaxy (from SDSS), the other, out of which the coolest result (in my own, not very humble opinion) was distilled was from the ZFOURGE survey. In that data set, there are “only” just under 400k galaxies, but there were very many properties known, such as brightnesses through 39 filters, derived properties such as the total mass in stars in them, the rate at which stars were formed, as well as an indicator whether or not the galaxies have an active nucleus, as determined from their properties in X-rays, radio, or infrared.

I decided to try something simple and take the full photometric set of columns, so the brightness of the objects in many many wavelengths as well as a measure of their distance to us into account and do some unsupervised machine learning on that data set. The data set had 45 dimensions, so an obvious first choice was to do some dimensionality reduction on it. I played with PCA and my favorite bit of magic: t-SNE. A dimensionality reduction algorithm like that is supposed to reveal if any substructure in the data is present. In short, it tends to conserve local structure and screw up global structure just enough to give a rather clear representation of any clumping in the original high dimensional data set, in two dimensions (or more, if you want, but two is easiest to visualize). I made this plot without putting in any knowledge about which galaxies are AGN, but colored the AGNs and made them a bit bigger, just to see where they would end up:
t-SNE representation of galaxy data from ZFOURGE

To me, it was absolutely astonishing to see how that simple first try came up with something that seems too good to be true. The AGN cluster within clumps that were identified without any knowledge of the galaxies having an active nucleus or not. Many galaxies in there are not classified as AGN. Is that because they were simply not observed at the right wavelengths? Or are they observed but would their flux be just below detectable levels? Are the few AGN far away from the rest possible mis-classifications? Enough questions to follow up!

On the fly, we needed to solve some pretty nasty problems in order to get to this point, and that’s exactly what makes these projects so much fun to do. In the data set, there were a lot of null values, no observed flux in some filters. This could either mean that the observatory that was supposed to measure that flux didn’t point in the direction of the objects (yet), or that there was no detected flux above the noise. Working with cells that have no number at all or only upper limits on the brightness in some of the features that were fed to the machine learning algorithm is something most ML models are not very good at. We made some simple approximations and informed guesses about what numbers to impute into the data set. Did that have any influence on the results? Likely! Hard to test though… For me, this has sprung a new investigation on how to deal with ML on data with upper or lower limits on some of the features. I might report on that some time in the future!

The hackathon was a huge success. It is a lot of fun to gather with people with a lot of different backgrounds to just sit together for two days and in fact get to useful results, and interesting questions for follow-up. Many of the projects had either some semi-finished product, or leads into interesting further investigation that wouldn’t fit in two days. All the data is available online and all code is uploaded to github. Open science for the win!

Leaving the field: becoming an extronomer

I wrote the post below roughly 5 years ago now. I quit my academic job in astrophysics, turned to industry and became a data scientist. I might at some point write something about how I think about all of this now.

I have decided to quit astronomy and start a job in the ‘real world’

I give up on a dream. I thoroughly enjoy doing astronomy. I have time left on my current contract and am even fairly confident that after this and another limited number of temporary jobs, I could have gotten a more permanent job in the field at some time, somewhere. So why quit? The uncertainty in a career in astronomy is enormous. If you don’t belong to the very top, and I don’t, you will have to go with the flow and move to wherever the field wants you. Sometimes that will get you to a very nice place in every respect (as we had in Baltimore), sometimes the place to work is very nice, but the place to live less so (like our current situation) and without a doubt even less desirable combinations are possible. Not the biggest deal for a short term postdoc (though too bad if it really doesn’t work out), but where will this long sought-after tenure-track job take you? And when?

Everybody who has done it for a while knows it: living far away from family and good friends is not easy. You can and will build up a new social life (if you even care about a social life, which you should), but those close at heart will be far. Too far, often. Our daughter deserves to grow up among the love of her grandparents and the rest of her family, just as well as they deserve to witness Amy growing up. It is a choice that everyone has to make for him-/herself, but for me a career in astronomy does not outweigh this aspect of life.

Contrary to (too) many academics, I believe that jobs outside of academia can be equally interesting. In many jobs, the everyday activities are even very similar to those of an astronomer. I think I have landed such a job. I will work in data science and business intelligence at a relatively small scale health insurance provider. An example of a project could be to detect fraud in their databases of claims, doctors, hospitals etc. (automatically). In my opinion, that is intellectually as challenging as the questions I am working on in astronomy, with the additional benefit that more people than just a handful of colleagues care about what you do.

Doing astronomy is fun. Like me, many colleagues often describe it as getting paid for your hobby. I can now go back to doing it purely as a hobby. There are several projects I will try to stay involved in to some extent, and I have a couple of very small projects in mind that I still can do. One doesn’t need to be a professional astronomer to do something fun and remotely useful. As an extronomer, you can easily be an amateur astrophysicist as well.

There are many aspects of working in astronomy that I will miss. The friendly atmosphere, collegiality and informality are a bless. I have met many great friends, with whom I hope to stay in contact. On the other hand, I am very much looking forward to my new profession and old environment. Even though I will leave the field professionally, at heart and in my way of thinking I will always be an astronomer.