May 18th 2015

Eagle-Eye Astronomy (FUN)

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This course introduces the observational technique of optical interferometry in astronomy, the most acute vision of the night sky, what we call "Eagle-Eye Astronomy".

This course introduces the observational technique of optical interferometry as it is currently used in astronomy. Starting from a simple description of the image formation process at work in a telescope, the phenomenon of interference will be revealed as central to an understanding of modern astronomical optics. Understanding this will grant you with the most acute vision of the night sky, what we call "eagle-eye astronomy".

Rather than a laundry list of facts and numbers to memorize about interferometry, the course uses interferometry as a pretext to explore the method at work during a scientific investigation: from the simple initial curiosity that leads to the formulation of a question to its resolution, via the specification of an instrumentation, the conduct and interpretation of observations.

The optical stellar interferometer will be demystified, and its characteristics and constraints: overall geometry, delay lines, coverage of the sky, sensitivity, imaging capability... will be introduced in a logical and progressive manner, that may even lead you to come up with your own ideas and concepts!

Interferometry produces raw data of a somewhat unusual type, called "visibilities", estimated from very astute measurements made by specially designed instruments. A fine understanding of the processes that contribute to these measurements leads to the production of near ideal observable quantities, combining precision and accuracy.

These measurements are then use to dress high fidelity models or images of often exotic sources: evolved stars reaching the last stages of their life, tightly interacting binary objects or still-forming planetary systems. The tools and methods covered in the course will give enough background for the students to feel comfortable with putting together their own observing programs in optical interferometry.

This is not a general public astronomy course: it focuses on a specific type of astronomical observation that is required when one needs high angular resolution information. The intended audience primarily consists of first or second year's Master's degree students with an interest in astronomy and/or astronomical instrumentation. Others, with a background in engineering should also feel quite comfortable.

At a tactical level, students should be familiar with complex numbers (used to describe electromagnetic waves), Taylor expansions (used to approximate and simplify complex equations) and have a basic understanding of statistics (mean, standard deviation).

Interferometry specialists are said to live in the "Fourier space": the Fourier Transform is a tool that indeed proves central to the course. While it will be introduced again and covered during this course, a preliminary understanding of what it is and how it works (at least in the 1-dimensional case) would prove useful.