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IfA Astronomers Win 2010 Humboldt Awards

Two IfA astronomers are the recipients of senior research awards from the Alexander von Humboldt Foundation in Germany. These research awards are intended to recognize the lifelong academic achievements of the awardees, are granted on the basis of nominations by eminent German scholars, and enable awardees to come to Germany to work on a research project with a German host.

IfA Director Rolf-Peter Kudritzki, who will relinquish the IfA directorship at the end of 2010, plans to use his Humboldt award during a 2011 sabbatical in Germany to investigate the physics of galaxies.

Drs. Bresolin and Kudritzki
Rolf-Peter Kudritzki (right) working with collaborator Fabio Bresolin.

Kudritzki will use the brightest stars in the Universe as tools to dissect galaxies. He will analyze spectra of hundreds of supergiant stars (stars with radii as large as 300 times the Sun and a hundred thousand times brighter) in distant galaxies. By applying completely new methods developed with his collaborators, who include IfA astronomers Fabio Bresolin and Miguel Urbaneja, Kudritzki will be able to use the spectra to determine the chemical compositions of galaxies and their distances from us. For instance, in spiral galaxies like our own Milky Way, the stars in the center have a higher percentage of elements heavier than hydrogen and helium than the stars at the edges of the rotating spiral arms.

Data about the chemical composition of galaxies can be used to test the present theory about how galaxies have formed in an expanding Universe that is dominated by cold dark matter (matter that does not interact with any form of light and whose constituent particles move more slowly than light) and dark energy (the mysterious force that is accelerating the expansion of the Universe). In fact, chemical analysis is one of the very few ways to test this scenario quantitatively. So far, the present knowledge of the chemical composition of spiral galaxies is very uncertain. Kudritzki's new method will be the first to provide accurate numbers.

"This project is entirely new. Nobody has ever done anything like this, except Fabio, Miguel, and me. Thus, I am truly excited and look forward to spending all my energy and time on it. I will use all the largest telescopes in the world for this project, including those on Mauna Kea and in Chile, and also the Hubble Space Telescope," Kudritzki said.

Jeff Kuhn
Jeff Kuhn

Jeff Kuhn received his award on the strength of his cumulative research studying the Sun. This is the first time that a solar scientist from the United States has been granted the prize. Kuhn's research has often focused on finding new ways to understand the solar interior by using observations of its surface made by instruments on the ground and in space. His group recently found that, unlike almost everything else that we measure about the Sun, it is constant in diameter to better than a few parts in a million. Kuhn said, "I plan to use this award to develop new models of how and why the solar cycle is so dependent on the death cycle of sunspots." He added that the physics is not known but critical to understanding how all stars evolve and change, and that "this understanding may ultimately help us predict how and when a changing Sun affects Earth's climate."

Pat Henry
Pat Henry

IfA astronomer J. Patrick Henry spent the spring in Germany on a Humboldt award that is a follow-up to the one he received in 2003. Henry is one of the world's experts on the cosmological evolution of clusters of galaxies. He pioneered the use of X-ray observations of clusters to understand how the entire Universe grows. His work provided some of the earliest evidence for what has become the standard description of that growth, including the idea that most matter in the Universe is dark matter. While in Germany, Henry finished a paper describing the properties of one of the most distant clusters of galaxies yet found. These very distant objects let astronomers actually see how clusters of galaxies are formed rather than deducing how they formed from studying the properties of fully grown examples.

IfA astronomer David Sanders is also a previous winner of a Humboldt research award.