Fermilab Today Thursday, September 6, 2007

Space telescope heads to dark energy finals

A rendering of the SuperNova/Acceleration Probe, one of three JDEM projects that could be funded by DOE and NASA. Image courtesy of SNAP

Fermilab scientists involved in the SNAP project found themselves Wednesday thrust into a likely three-way race to take the lead as one of the nation's top astrophysics research projects for the next decade.

The National Research Council announced its priorities for moving forward with research in the five proposed Beyond Einstein Missions: Constellation X, Laser Interferometer Space Antenna, Joint Dark Energy Mission, Inflation Probe and Black Hole Finder Probe.

NASA, DOE, Congress and the Office of Science and Technology Policy asked for the committee assessment for Beyond Einstein, NASA's research roadmap for astrophysics.

The commission, which studied the programs, recommended as its first priority that NASA and DOE pursue JDEM because of its potential for broad scientific impact and because it is the "most technically feasible option for immediate development." The commission also recommended an immediate JDEM proposal competition to prepare for a start in 2009.

The winning project may be one of the three studied by the committee or a new proposal, the committee said. The winning project could get up to a recommended $400 million in funding from DOE as well as funding from NASA, according to the committee report.

Fermilab plays a key role in the JDEM project SuperNova/Acceleration Probe, dubbed SNAP. The other JDEM projects are Advanced Dark Energy Physics Telescope, dubbed ADEPT and Dark Energy Space Telescope, DESTINY.

All three projects seek to explain the accelerating expansion of the universe by discovering the nature of dark energy. By tracking the explosions across the sky, scientists create a map of the universe, analogous to tree rings. The distance between explosions marks the age and growth period, just as the rings do on a tree trunk.

"One of the advantages of SNAP is we started first," said Tom Diehl, of the PPD and cospokesman of the Fermilab SNAP effort. "We are closer to a nuts and bolts finished project - a telescope."

Work on SNAP started in 2000 with Fermilab joining in about 2003. SNAP could have a telescope ready to launch by the middle of the next decade. The project involves 160 scientists, including 16 at Fermilab.

A strength of SNAP is that it employs more than one method of studying the dark energy thought to be fueling the expansion. Fermilab theorists helped formulated the two main methods. The Supernova search repeatedly scans a small area of the sky looking for supernova explosions. The weak lensing search looks at a 1,000 square mile section of sky to measure the distortion of galaxies to assess the density and location of matter that clumped together after the Big Bang. Results from the two research tactics should present a similar picture of how the universe expanded after the Big Bang, then started to slow as matter clumped together and then accelerated expansion again, theoretically because of the pressure of dark energy, Diehl said.

If the theory is correct, it would prove the existence of physics beyond the Standard Model, which does not incorporate dark energy or dark matter.

"It is a new piece of physics that is really unknown so we are just starting to characterize it," said Steve Kent, of the Computing Division and cospokesman of the Fermilab SNAP effort. "We think SNAP is just the most aggressive, having two solid competing methods of discovering dark energy. It is really a better bang for the buck."

Berkeley Laboratory heads up the SNAP project and was one of two teams to first discover dark energy from supernovae's that drives the research. Still, Fermilab plays several key roles in project development. SNAP essentially is a space telescope with a camera on it. Fermilab is helping assemble the detectors that collect the light to create the images and is providing the electronics to organize and store the images of data. During the last three years, scientist have done radiation testing on the image system to make sure that radiation from the sun and cosmic rays won't cause the system to lose data.

Fermilab also has created software to simulate the camera's operation in space to work through potential problems and come up strategies for calibrating the detectors using well-measured stars.

--Tona Kunz

Read the National Academies press release here.

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