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Tiina Suomijärvi


Breaking the Rays



© Tiina Suomijärvi

Still water runs deep. Tiina Suomijärvi, Professor of Astroparticles at the Nuclear Physics Institute (IPN)1 in Orsay, may seem calm and collected, yet she has quite the personality. She is as energetic as the particles she studies. She enjoys getting to the bottom of things, be it the ocean (she's an avid diver) or the core of matter. When she left Finland for France in 1983 for an internship at CEA (France's Atomic Energy Center), she already had her Masters in nuclear physics. But she extended her stay in France, for more “personal” reasons, she says gracefully. She signed up at Université Paris-XI to prepare her thesis in nuclear physics. “At first, I worked on low-energy reactions and how to model them,” she recalls. She joined IPN after receiving her PhD, and in 1988 was appointed Associate Professor at Université Paris-XI. In 1994, she went to Michigan State University to study unstable nuclei and more specifically the “exotic” variety,2 using radioactive waves. “When I returned to IPN, I focused entirely on the reactions induced by radioactive waves,” she says. But the world had become too small for this long-distance traveler: She decided to explore the universe.

In 1999, Suomijärvi changed from experimental nuclear physics to astroparticle physics. She founded an astroparticle research group at IPN and joined the Pierre Auger international experiment,3 where she studies the ultrahigh energy cosmic rays that reach the Earth. “We know they exist because they have been observed, but we don't know where they come from. Are they accelerated in extremely violent astrophysical objects such as the active cores of galaxies? It is one of the mysteries of modern astrophysics,” she points out. Located in the Pampas of central Argentina, the Pierre Auger Observatory is her hunting ground. Its 3000 sq. kilometer network of ground sensors traps the ultrahigh energy cosmic rays that she tracks incessantly. “The rays are very rare–only one per square kilometer and per century!–so catching a glimpse of them is rather difficult,” she adds. “When those particles arrive in the Earth's atmosphere, they react by disintegrating into several billion secondary particles and by creating cosmic ray showers.”

When she is not at the Pierre Auger Observatory where she coordinates and manages electronic development, she does research, publishes, teaches, supervises PhD students, gives courses and conferences, and makes scientific presentations to the general public. Speaking five languages, she works on large-scale European research projects. Suomijärvi is also very involved in the creation of a second Pierre Auger observatory in Colorado, that will scrutinize the sky in the northern hemisphere. “When you work with astroparticles, you are constantly reminded that we are insignificant on the scale of the universe, and that there is still much to discover,” adds the physicist, becoming a little... metaphysical.


Laetitia Louis-Hommani




Notes :

1. Institut CNRS / Université Paris-XI.
2. Unstable nuclei in outer space that can be created in a particle accelerator.
3. The Auger Observatory is a “hybrid detector,” using two independent methods to detect and study high-energy cosmic rays. View web site

Contacts :

Tiina Suomijärvi
Institut de physique nucléaire d'Orsay.


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