Rich NorbyEcologist Rich Norby works to integrate experiments, models

Rich Norby, an ecologist at DOE's  Oak Ridge National Laboratory, has spent his career exploring how ecosystems respond to atmospheric and climate change, including more than a decade studying the effects of elevated carbon dioxide in a Tennessee sweetgum forest as part of the Free-Air CO2 Enrichment (FACE) project at ORNL.

“When you work with forests, the questions are many decades long,” Norby said.

After the ORNL FACE experiment measurements were completed in 2009, Norby and colleagues integrated the mounds of observational data into computer models.

“We can’t do experiments directly to address all the questions related to global forest response over many decades,” he said. “So we have to make use of models to get at these questions. An important reason for intensive experiments is to inform and improve our models.”

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In this still from a simulation, a Type Ia supernova explodes (dark brown color). The supernova material is ejected outwards at a velocity of about 10,000 km/s. The ejected material then slams into its companion star (light blue color). The violent collision produces an ultraviolet pulse that is emitted from the conical hole carved out by the companion star. Credit: Courtesy of Daniel KasenSupernova hunting with supercomputers

Type Ia supernovae are famous for their consistency. Ironically, new observations suggest that their origins may not be uniform at all. Using a “roadmap” of theoretical calculations and supercomputer simulations, astronomers observed for the first time a flash of light caused by a supernova slamming into a nearby star, allowing them to determine the stellar system from which the supernova was born. This finding confirms one of two competing theories about the birth of Type Ia supernovae. But taken with other observations, the results imply that there could be two distinct populations of these objects. The details of these findings appear May 20 in an advance online issue of Nature.

“By calibrating the relative brightness of Type Ia supernovae to several percent accuracy, astronomers were able to use them to discover the acceleration of the Universe. But if we want to push further and constrain the detailed properties of the dark energy driving acceleration, we need more accurate measurements. If we don’t know where Type Ia supernovae come from, we can’t be totally confident that our cosmological measurements are correct,” says Daniel Kasen, an Associate Professor of Astronomy and Physics at UC Berkeley, who holds a joint appointment at DOE's Lawrence Berkeley National Laboratory (Berkeley Lab).

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See also…

DOE Pulse
  • Number 440  |
  • June 1, 2015
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