Paczynski dies of brain cancer

Astrophysical sciences professor Bohdan Paczynski, pioneer of a technique that led to the discovery of several planets outside Earth's solar system, died of brain cancer last week at the age of 67.

Paczynski, who was born and educated in Poland and joined the Princeton faculty in 1982, was known by his colleagues and students as a brilliant scientist and inspirational teacher.

"He was one of the world's greatest astrophysicists, recognized as the world authority on stellar structure and evolution," astrophysics professor Bruce Draine said. "He was inspiring to the rest of us, who tried to emulate his clarity of thought."

Paczynski developed applications of gravitational lensing, an effect discovered by Einstein, in which a massive object focuses light from a more distant object, causing the distant object to appear brighter.

The application allows scientists to detect the presence of planets around distant stars by measuring changes in the brightness of the stars, and several new planets have been discovered using this method, including in 2005 the first earthlike planet outside the solar system.

Gravitational lensing also helped prove the existence of dark matter, an unknown material that makes up most of the mass of the universe.

Among his other achievements, Paczynski determined that intense gamma-ray bursts originate outside the Milky Way galaxy, contrary to the conventional wisdom, which stated that they originated within the galaxy. "He often used very clever techniques to really get new insights about the nature of stars," astrophysics professor David Spergel said.

Colleagues said Paczynski did not hesitate to go against conventional wisdom in astrophysical sciences. "Gravitational lensing was regarded as a curiosity by many people. People thought it would be a rare phenomenon," Draine said. "He proved that it was feasible to use existing technology to observe and use it."

Paczynski's theories about gamma-ray sources were radical at the time of their conception. "When he wrote those papers, at first all the experts said he went a bit over the edge, and today we can look back and see that he was correct," Michael Strauss, a professor of astrophysical sciences, said.

Even with his successes in the United States, colleagues emphasized Paczynski's lasting bonds to his home country. "He had very strong ties to the Polish astronomical community and brought a lot of Polish astronomers to the U.S.," Strauss said. In addition to working at facilities in the United States and Australia, Paczynski used Polish observatories in many of his experiments.

Spergel remembers Paczynski best for his participation in morning discussions with astrophysics professors and students. "Paczynski was always there, leading the discussion. He was always a source of new ideas and new insights."

Strauss emphasized that Paczynski "was extremely good at working with students." When assigning projects to graduate students, "he was capable of thinking of clever ideas ... and his projects always finished beautifully within one semester."

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"I was always impressed with the clarity with which he would introduce new topics and the modesty and warmth with which he communicated with all of us," Zachory Berta '07 said.