Participants in the XXVI Winter School of the IAC in their first class with Professor Tom Loredo (Cornell University, USA) Credit: Miguel Briganti, SMM (IAC).
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Since 1989 the Astrophysics Institute of the Canaries (IAC), Centre of Excellence "Severo Ochoa" organizes every year an International Winter School in Astrophysics, which lasts for two weeks. This, the twenty sixth school, which is being in collaboration with the UniversityofLaLagunaand celebrated from 3rd to 14th November at the IAC Headquarters in La Laguna, will be attended by some forty young astrophysicists -doctoral students and postdocs in Astrophysics- from ten countries (Italy, México, Poland, Venezuela, Slovenia, Finland, South Africa, Germany, Iran, and Spain), who will receive classes from seven lecturers, who are experts in statistics applied to astrophysics.

During the course of these Winter Schools, the students get the opportunity to be brought up to date in depth on a current theme of greatastronomicalinterest,toexchangeknowledgewiththe top specialists in Astrophysics, and to visit the Canary Island Observatories. On thisoccasionthey will visit the Teide Observatory on Wednesday 12th November.

The Director of the IAC, Rafael Rebolo, welcomed the students and lecturers this morning. He talked about the work carried out at the Institute and its Observatories, and of the Divisions in which they are organized: Research, Postgraduate Studies, Instrumentation, and Administration. He mentioned the varied lines of research, as well as the projectsforthedesignandconstruction of instruments for telescopes. He reminded his audience that the IAC was one of the pioneers in the use ofBayesianinference,aslongagoasthenineteen-nineties,inthecontextofthestudiesof the cosmic microwave background which were than being performed with a number of different telescopes at the Teide Observatory.

As in previous Winter Schools, the material given in the classes willbepublishedasabookbythe Scientific Publishers Cambridge University Press.

Detective work

In spite of being an observational science, it is clear that Astrophysics cannot study objects directly, as if we were measuring a table: "All the information available to us" says Íñigo Arregui, researcher at the IAC, andco-organizerofthisschool,"isindirect,basedontheobservationofthe behaviour of light. This means that there is always a degree of uncertainty in the data. With Bayesian inference it is possible to combine the data available foranobjectoraphenomenon,so that we finally obtain an idea closest to the correct one". That is to say that to obtain a credible idea of reality we must combine all the available data, and do so in such a way that we can continue updating our models as new information comes in.

"We can compare this" continues Arregui, "with the work of a detective who is collecting data during an investigation. As he collects more and more data, he builds a model inhisheadofhow the events could have taken place; he updates the model every time he makes a new finding. If the detective has several suspects he will keep on updating the probability that each one is the murderer according to this mental model. Applied to Astrophysics" he concludes, " the suspects are the hypotheses, and the data are the information gathered by the instruments and telescopes".

What distinguishes Bayesian inference from conventional inference is, therefore, its capacity to work with a large quantity of data, in practice all the data available. For example, using conventional statistics wecouldknowtheprobabilityofanaccidentforamanoversixtyyearsold, and a car with 100 horsepower. But when the insurance company has to work out the premium for this hypothetical male it not only has to take into account his gender and age, but also his history of accidents, that of people with the same characteristics as him, the degree ofdangerof the roads in his area, and innumerable other factors which they also have to update asnewdata arrive. This is done using Bayesian inference.

Organizing Committee: Andrés Asensio Ramos, Íñigo Arregui, Antonio Aparicio y Rafael Rebolo.

Secretary: Lourdes González.

Contacts: Andrés Asensio Ramos (IAC): aasensio [at] y 922605238 Íñigo Arregui (IAC): iarregui [at] y 922605465

Press: Carmen del Puerto: prensa [at] y 922605208

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