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Christmas at La Silla

The control room of the Euler Telescope in La Silla. (Photo: Pierre Bratschi)

The control room of the Euler Telescope in La Silla. (Photo: Manuela Rimbault)

By Pierre Bratschi

On Wednesday 16th December, a Christmas tree with fake snow in the middle of summer welcomed me under a blazing sun at my arrival in La Silla. “That’s the tradition every year, and it is deeply rooted here,” explained Mario, an ESO employee in charge of the rooms’ maintenance, “and as you will see, on Christmas Day, all employees’ children spend the day with their parents here.” This year it was my turn to spend the Christmas Euler Swiss telescope mission in la Silla. Euler is a 1.2m diameter telescope built and maintained by the Observatory of Geneva University. It has been operating since 1998 and is mainly dedicated to the hunt for exoplanets. The telescope is equipped with CORALIE, a spectrograph capable of measuring the radial velocity with an accuracy better than 5 m/s and a CCD camera to observe transits and lensing.

A mission usually lasts 14 days, or rather 14 nights, to be precise. The pace of work is modelled on the schedule of the sun, and although the nights are shorter in summer, the probability of having clear nights during that season is higher. As proof of this, during this Christmas 2015 mission, I didn’t see any clouds for two weeks while a colleague of mine had only five usable nights out of sixteen during her August mission. She didn’t have any luck and I had an exceptional period. “This is because of El Nino, which is very strong this year,” explained Alejandro, a telescope assistant at the site.

Going to La Silla is a bit like taking holy orders, as we are there only to focus on astronomy. The ESO staff relieves us from everyday life constraints such as cooking, bedroom cleaning and laundry. Everything is organized for us to concentrate only on our observations. However, the following proved to be particularly difficult for me: having to sleep during the day and trying to resist the food temptation at the risk of returning to Switzerland with a few extra kilos. Indeed, the restaurant opens 24 hours a day, and if no one is present to serve, you can just help yourself, and everything is good!

Barbecue in the desert. (Photo: Pierre Bratschi)

The barbecue at La Silla. (Photo: Manuela Rimbault)

Once installed in that rhythm I was gradually forgetting what real “civil” life was and for that reason Christmas at La Silla had a special taste to me. The employees and their families met in the restaurant decorated for the occasion. The imposing grill was lit for a giant barbecue and, for this unique time of the year, you could enjoy a delicious wine of which only Chileans detain the secret. This year they served Merlot. Sadly, at 20:30 it was already time for me to go to the telescope, which is about one kilometre away from the restaurant, to begin my observations at 21:30.

Unlike my colleagues of NCCR PlanetS and the Observatory, I didn’t have any personal programme, so I observed for the community and tried to spread the observations as equitably as possible. On the menu, a Geneva speciality was offered to me: radial velocities. Christmas night, like all other nights, ended at 6:30, and despite the advanced instrumentation that was at my disposal I didn’t see Santa Claus.

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