Professor seeks and finds solar systems' missing links

Professor of Physics and Astronomy David Koerner wouldn't mind finding life outside of Earth's atmosphere, but for now he'll settle on discovering the solar system around the star HR4796.

Koerner led a team at Keck Observatory on Mauna Kea, Hawaii, that photographed dust and gas rotating and configuring in a disk around the star last April. The dust around the outside, hole in the middle and bright spot at its center gave astronomers the most definitive view of a solar system to date and clues about how our own system formed.


David Koerner with an image of the Owens Valley Array, a radio telescope he has used in his searches.

Photo by Kim Weiner

Koerner and others had known of this occurrence for some time-he had spent most of his post-doc years at the Jet Propulsion Laboratory observing hints of them-yet had never been able to view it without the brightness of stars obscuring surrounding areas.

Before coming to Penn last year, Koerner worked at JPL and UCLA, using various telescopes to detect emissions from disks. He had even used Keck over three semesters but saw little due to poor weather and an improperly functioning telescope.

Given another chance to use the observatory through NASA's Origins Program, Koerner and his associates brought MIRLIN (a high-resolution mid-infrared camera developed by his colleague Michael Ressler) and, as Koerner put it, "We hit pay dirt." After starting at dusk, by 3 a.m. the team had grown weary of looking where they knew the formation was.

"You expect a certain brightness from a star and we didn't see it," Koerner explained.

"By this time my partner was exhausted so he said, 'you drive.'"

Koerner performed the highly technical equivalent of taking off the lens cap. "I turned up the integration time and there it was, right where we had been looking."

Koerner was scheduled to view the same area two days later using the Hubble Space Telescope when he realized the NASA team had been looking in the same direction he was. They must have seen the same thing but didn't know it. "I had to make an ethical decision: if I wanted to be a bad guy. I called their principal investigator and said, 'Look at your data.' They still didn't see it. Our contrast image was much more telling. Once they re-analyzed it with the right star subtraction, they saw it."

Koerner is still analyzing images and data taken from Hubble, trying to determine whether any of the dust on the edges of the disk contains organic material and, eventually, whether that material has or could find a home on planets. In addition to being one of the more important breakthoughs in history, such a finding would provide material for his "Life in the Universe" course, a class he devotes to recognizing the elements that make life feasible.

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Originally published on January 28, 1999