Penn researchers take the lead in Dark Energy Survey

For Penn professors studying dark energy, pictures of space are not only aesthetically pleasing, but also scientifically significant in astrophysics.

Several Penn researchers have been involved as leaders in the Dark Energy Survey, an international project launched on Aug. 31 whose goal is to analyze the properties of dark energy — a generic term that explains why the universe’s expansion is accelerating, contrary to the laws of gravity. The survey has received participants from 25 research organizations across six countries.

The project uses a specially designed camera attached to an existing telescope in Chile to take wide-angle images of the sky in multiple colors and to deep depth and analyzes them using advanced algorithms that Penn researchers have developed. The project’s goal is to collect images of millions of galaxies and thousands of supernovae over the course of five years.

“It is natural to expect that the expansion of the universe should slow down over time because of the mutual gravitations of the galaxies,” physics professor Mark Trodden explained in an email about the significance of this work with dark energy.

“However, 15 years ago it was discovered that the opposite is true,” Trodden said, adding that this discovery posed “a sharp question to fundamental physics.”

“There’s no way we can escape needing to understand [dark energy] if we want to explain physical reality,” physics professor Larry Gladney said.

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As part of the Penn team working on this project, Gladney and his colleagues are mainly responsible for creating the algorithm that would create and sort through the catalogue of pictures of the universe. Penn’s reputation for high-level research in both particle physics and cosmology makes it a natural candidate to be invited to a project like this, Gladney said.

Gladney also noted that he and his team must be familiar with various fields, such as astronomy, computer science and statistics, in order to “use large data sets as a way of getting at new science.”

To get at this “new science,” he and his team will be comparing the shapes of galaxies and the measured versus expected distances of particular types of supernovae, to examine the properties of dark energy — and how it is causing the expansion of the universe.

Although he was first trained as a particle physicist, Gladney switched his research focus to the larger scale of astronomy when “the time came that [he] could seek new particles and new forms of energy through telescopes that we may never be able to make in the laboratory.”

“I’ve always been interested in knowing what the most fundamental stuff of the universe is,” he said. “Like any scientist, I’m not defined so much by the label on my Ph.D. as by the questions that motivate me. I’ll use whatever methods or instruments I can to seek answers.”

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