It is 6 a.m. The sky is still dark outside. My doorbell rings. It is the taxi that will drive me to Santiago airport to catch the early plane to Antofagasta in northern Chile. After a flight up the spine of Chile lasting an hour and 40 minutes, the journey is not yet over. My destination is the Paranal Observatory in the Atacama Desert, which is still a two-hour bus ride away and literally in the middle of nowhere. The last hour of the drive crosses an endless, Mars-like landscape of brown-red hills scattered with massive rocks, detaching me from my usual world and dropping me into a somehow different dimension.

Operated by the European Southern Observatory (ESO), Paranal is among the biggest observatories in the world, with four 8 m telescopes. While I am working there, time seems to flow differently, and I soon forget which day of the week it is. As an astronomer, I work during the night, from sunset to sunrise. It is easy to work too hard, and I am away from my family and my usual life one or two weeks every month, amassing over 100 nights per year at the observatory.

It is simple to explain why astronomers build observatories in such remote places: the total absence of light pollution, lots of clear-sky nights, good “seeing” (image quality) and extremely low humidity, which is critical for observing in the near-infrared part of the spectrum. But why people end up working in such places is a little more complicated. Although astronomers are sometimes pictured as nerds with few social skills, keen to isolate themselves in the company of books and complicated formulas, in fact, places like Paranal exist because they are where astronomy can best be done. Most of the astronomers I meet are quite normal and most work in universities with a regular nineto- five routine, only travelling to remote places a handful of times each year to do their observations.

Although Paranal is an isolated place, it is also a little village where about 100 people live at any given time. Most of these “villagers” are not even astronomers, but engineers, technicians, administrators and people working on catering and services. They work (a lot!) during the day and relax during the evening in the gym, in the cinema room, at the pool table or in the sauna. It is a bizarre place that works hard to appear normal.

Beyond the ends of the Earth

When I applied for a fellowship at Paranal seven years ago, I was unaware of all these things. I just knew that Paranal existed, and I wanted to work there. Before that, I had earned a Master’s degree in astronomy at the University of Padova in Italy, where Galileo Galilei himself taught about 400 years ago. I then did a PhD in astrophysics at the University of Wyoming in the US, but even after that I had still not gained much experience actually doing observations. So, I decided to fill in this gap by applying for an ESO postdoc position at Paranal.

By the time I applied for a longer-term staff position in 2004, I was familiar with the place. I had become used to its dryness (my skin had not, though), and I had started liking and enjoying that Martian landscape so much that a hike across the desert is now a magical break from the working routine. I had even decided that I much preferred to observe at night and take care of an instrument than to teach (I actually said this at my job interview). So, here I am.

Within the constraint of needing to work 105 nights per year at Paranal in 7–14 night stretches, an individual’s schedule at ESO can be quite flexible, allowing us to participate in conferences, work at other observatories and get involved in collaborations. When I am not doing observations, I work on my scientific research at ESO’s offices in Vitacura, Santiago. I am interested in cataclysmic variable stars, which are interacting binary systems where a white dwarf (a dead star) accretes matter from a “cold sun”. Such systems display all kinds of variability phenomena, ranging from the small, rapid, random variations in brightness (“flickering”) that characterize the ongoing mass transfer to a sudden increase in luminosity (“outburst”). My time in Vitacura allows me to analyse my variability data and also go to seminars, journal clubs and coffee breaks where I can discuss results, progress or problems with other astronomers.

When I am at Paranal, however, I mostly forget about my research and focus on performing observations with one of the telescopes. Each telescope is equipped with three instruments. For example, one telescope hosts the near-infrared (NIR) instruments NaCo (a imager and spectrograph), SINFONI (an integral field unit spectrograph) and HAWK-I (a wide-field imager). NaCo and SINFONI are adaptive-optics-assisted instruments that can either use a real star or a laser-generated one to correct the wavefront. During a night of observing, we astronomers decide which of several programmes or projects we want to carry out and set up the relevant instrument to “stare” at the target object, recording almost every photon that hits the telescope. We then classify the results according to their quality with respect to certain requirements.

The technical side

Paranal is quite special in that most of the observations are done by staff astronomers, like me, working in “service mode”, which means that we perform observations for users (such as astronomers based at universities) without requiring them to do the work in person. This guarantees the best sky conditions to the work that needs them most; in a given night, we can execute several different programmes for different users, although we will not necessarily complete them in a single night. At smaller observatories, in contrast, the person who makes a proposal for telescope time must perform their own observations.

Occasionally during an observing night I feel like I am part of an assembly line. Sometimes the observations being carried out are interesting and/or challenging enough to get me excited. Other times, I just hope for long and boring observations that require little attention so that I can catch up on tasks like creating documentation for the instrument’s users or evaluating the technical feasibility of the proposed observations. Occasionally, a night shift is used to train newcomers, and this is both fun and a good test of expertise.

However, the most interesting nights are the technical ones, when my colleagues and I have to perform tests with the instrument that we are responsible for — either because it has experienced a major failure and needs to be fixed or recalibrated, or because it is a brand new instrument just arrived at the observatory and so needs to be properly characterized before offering it as an option to the user community. For example, we are currently commissioning a new instrument called X-shooter, which is a composite spectrograph that can deliver, within a single observation, a spectrum from the very blue to the near infrared (wavelengths from 300 to 2500 nm). An instrument with such a wide spectral coverage is bliss for all astronomers interested in the spectral-energy distribution and/or the redshift of targets like gamma-ray bursts, supernovae, close binary systems, white and brown dwarf stars, and many other sky objects.

Commissioning an instrument requires a dedicated team of 5–10 people at the observatory itself, not counting the many others who work on the instrument’s design or construction. This team takes care of aligning the instrument optics, defining the reference position of its various functions, digging into and debugging the software, testing it on the sky, and finally reducing and analysing the data to verify that the instrument is performing as expected. This can take every night of a full whole two-week shift, and typically two or three such shifts are needed to complete the commissioning.

Once my shift is over, I return to Santiago, usually arriving home at night after another half a day of travel. My sleep patterns are mixed up for the next few days, and I sometimes fall asleep at random times. I usually feel okay, but if I try to do some sport, for example, I discover that my body is not yet back to normal. At work, I might forget why I have given a file a particular name. It is at these times that I feel like my research is progressing two steps forward and one back, but this is probably part of the game. By taking it easy, I slowly get back to a regular life, and I am once again able to think about the science. Now, where was I with my paper about Nova Scorpii 2008?