A visit to Oxford

Students going to the House of Exams in Oxford

Working at ESO gives great professional and social opportunities. Being at the center of European experimental astronomy, is the place where many new and exciting things take place. For this reason it attracts scientists and engineers from all over the world and this gives ESO staff the chance to exchange ideas, share views and start new and productive collaborations. Not only. ESO supports its Faculty members in traveling around the world to attend international conferences, and it encourages them to spend some of their time in science leaves in a research institutes of their choice. This is very important, since it allows ESO astronomers to concentrate on specific aspects of their scientific activity without being distracted by the daily functional duties related to the operational necessities of the organization.

Back in 2006 I had started an international collaboration on the stellar systems that are supposed to give rise to Type Ia Supernovae, those extremely luminous explosive events that are being used to probe the past history of the universe and its geometry (I will soon publish an article on this work in the CosmicDiary. The original publication can be seen here). This still ongoing collaboration has involved experts in different fields of supernova research, such as explosion physics, circumstellar and interstellar medium, binary stellar systems, stellar evolution and so on. One of the key roles in the success of this project has been played by the group led by Philipp Podsiadlowski, professor at the Department of Astrophysics of the Oxford University and tutorial fellow in Physics at St. Edmund Hall College.

According to the favorite scenario for the origin of Type Ia Supernovae, these explosions occur in a binary system, where a withe dwarf accretes material from a companion donor star. Matter in the white dwarf is in a very special condition (that physicists indicate as degenerate) and the density is extremely high (although not so high as in a neutron star). When the mass of the star reaches a critical limit (called the Chandrasekhar mass) the star undergoes a thermonuclear explosion that completely disrupts it and ejects all of its material into the surrounding space, at speeds that exceed 10,000 km per second.

Working at the Denys Wilkinson Building, with a nice view on the Parks of the University of Oxford.

Phil is an expert in binary star evolution and has been working a lot on Supernovae in general and on Type Ia in particular. During our collaboration, he has pointed out that a binary system, known as RS Ophiuchi, might be of great interest for our purposes. This is why we have started a new investigation to better understand the circumstellar environment of this intriguing system, which is most likely hosting a white dwarf with a mass very close to the Chandrasekhar limit. Therefore, last year I have decided to pay a visit to Phil in Oxford. And here I am. Most of you probably know the place already. Oxford is a very nice town, where you breath the academic life everywhere. You can still feel the presence of J.R.R. Tolkien, C.S. Lewis, L. Carroll… indeed a magic atmosphere. Then, if you have the chance to come not as a tourist, you will see even more exclusive corners of Oxford.

Prof. R. Pierrehumbert giving the 2009 Halley Lecture at the Martin Wood Lecture Theater - Oxford.

The days here have been very interesting, from several points of view. Besides specific discussions on the main topic and the prospect of our collaboration, many other stimulating events took place during my stay. For instance the science coffees of the Stellar Group, which take place every day at 11:00. During these meetings very different and sometimes random topics come up, leaving everybody free to throw her/his own ideas to the wall, in a way that is rather typical of astronomers (and scientists in general, I suppose) when they get together. Then, there were also a couple of, I would say, more exceptional events. The first one was the 2009 Halley Lecture here at the Department of Physics, a few hundred meters away from the Denys Wilkinson Building were I am sitting. When I arrived, Phil gave me an invitation and I was immediately struck by an intriguing coincidence. A few months ago I have been asked to give a public seminar on biodiversity in the universe. Well, that is not exactly my field and so I have started studying the subject, reading papers and books on this topic. One if them, which I am currently reading and I brought with me here in Oxford, is Rare Earth: Why Complex Life Is Uncommon in the Universe (2000), by P. Ward and D.E. Brownlee, which has introduced the Rare Earth Hypothesis. Guess what? The title of the Halley Lecture was “How rare is the Earth? Habitability in the Universe Reconsidered“. Amazing. The lecturer was Prof. Raymond Pierrehumbert from the University of Chicago. I was not sure, but that name did not sound new to me. In fact, he is the co-author of an important paper cited in the Ward-Brownlee book (Forget, F. and Pierrehumbert R.T. 1997: Warming Early Mars with carbon dioxide clouds that scatter infrared radiation. Science 278, 1273 – 1276), as I could verify when I got back home that evening. The world is small.

Prof. Philipp Podsiadlowski at St. Edmund Hall.

But the most unusual experience was probably the Friday dinner at St. Edmund Hall College. All Oxford colleges have very old traditions and, on Fridays, at St. Edmund Hall the fellows get together for dinner to which they can invite their guests too. So, I dressed up (Phil told me that jacket and tie would be highly appreciated) and with some trepidation I went down High Street (The High), turned left at Queen’s Lane and entered the ancient arch that leads into the internal court of St. Edmund Hall. Katrien Steenbrugge, fellow at St. John’s College, whom I met during the Stellar Coffee meeting on my first day in Oxford, was already there. She was wearing the typical academic gown of the University of Oxford. After a few minutes, Phil comes to welcome us, also wearing his gown. During the last days the weather was wonderful, but today it turned to what I am told is more typical of Oxford. That helps in bringing me back in time and it creates the proper atmosphere for the evening (Harry Potter style…). After visiting the internal park and the beautiful library (where lots of students are still busy reading and studying), we go to the dinner reception, where I am introduced to a number of fellows and guests. Fortunately I see another known face: Chris Wolf, member of the group led by Philipp, is also there, and I immediately join him for a drink. He explains to me many of the things I see but I do not understand. I am terrified by the thought I will break some of the very old traditions (I still managed to do so later on with one of them…). After a while a bell rings and we are all invited to move to the dining hall. Before starting, using a ceremonial hammer, the Principal, Prof. M. Mingos, proclaims the old formula “Benedictus Benedicat“, after which dinner officially starts. I am sitting close to Prof. A. Borthwick, who has also a guest, from China. After a while we end up talking about their field of work, that is hydraulic engineering. Since they mention floods and similar things, it comes to my mind that very recently I had read a report about the Vajont disaster, that occurred in the area were I come from, back in 1963. Of course they knew a lot about it and that made me think, once more, how small the world is.

After dinner (which ends with the “Benedicto Benedicatur” formula proclaimed by the Principal), we move to the next phase, which is called “the dessert” (but I was told that it is not exactly what the word would seem to imply). According to the rules, Prof. Borthwick makes sure that everybody gets a seat in such a way that she/he is not sitting close to the same people, so to maximize the interaction. But I also understand I should not be left alone (I guess to prevent some major trouble with my ignorance of the rules ;-). So, now I have Philipp on one side and the Principal on the other. Wine, fruit, chocolate and other sweets are circulated (strictly clockwise) along the table while we chat about our activities. But the interesting part comes afterwards, when we move to the tea and coffee room, and a disordered discussion about black holes and cosmology starts. There are several college fellows and guests and the discussion proceeds half serious and half funny, touching many interesting aspects (like the total momentum of the Universe), and ending with the existence of God. After quoting my good friend Glauco Venier, jazz pianist and composer (who said to me “if Bach exists, then God must exist “), I decide it is time to go. Katrien comes with me; it is half past midnight and it rains. We share Katrien’s umbrella walking along The High and we eventually part.

Days go by fast. Sitting in the office of Prof. Steve Rawlings (he is away for some days) I manage to finish the revision of a manuscript on the spectropolarimetry of SN2006X, a bright Type Ia Supernova we have studied with the ESO Very Large Telescope. I had given an informal discussion about it during my first day here in Oxford. And it is now with great pleasure, after quite a long time and intense discussions with the co-authors of the paper, that I finally re-submit it to the European journal Astronomy & Astrophysics. It contains some nice results about the chemical asymmetries in SN explosions and it took us quite an effort to put it together.

During my last day I am giving a colloquium on the progenitors of Type Ia Supernovae, the topic I have been busy with during the last few years. The tradition here is that the colloquium speaker is taken out for lunch by the students. And I made no exception. I enjoyed very much joining them at the pub where C.S. Lewis, good friend and colleague of J.R.R. Tolkien, used to go when he was living and teaching here in Oxford. Once the lunch is over, we go back to the institute. I have just some time to go quickly through the presentation that is already tea time. After a while, Mark Sullivan, who organizes the Colloquia, leads me down to the Dennis Sciama Lecture Theater. I spare you the details of the talk, since I will soon post an article on this very topic in the CosmicDiary. After the colloquium, there is wine and cheese (this is also typical of many academic institutes) after which we all go to a pub for a beer. My family, who has been enjoying Oxford during all these days, joins us. After a very nice and entertaining dinner (at a very good Italian restaurant), we finally part. I must say it is a bit sad. Everything worked so fine that we are indeed sorry to leave. It has been an intense, stimulating intellectual and social experience, certainly worth to be repeated. Thank you very much Phil, Chris, Mark, Katrien and all the fellows and students I met. Good bye, Oxford!

Mark Sullivan introduces my talk in the Dennis Sciama Lecture Theater