Baltimore astrophysicist strengthens 'dark energy' theory

Scientist uses Hubble to rule out competing theory

The Baltimore astrophysicist credited with discovering "dark energy," the mysterious force believed to be accelerating the expansion of the universe, says he has used the Hubble Space Telescope to disprove a competing explanation for the phenomenon.

Adam Riess, of the Johns Hopkins University and the Space Telescope Science Institute, says his team, using Hubble's new Wide Field Camera 3, was able to look at more stars, in both visible and infrared wavelengths. That eliminated errors introduced in previous work, which compared measurements from Hubble and other telescopes.

The refined numbers, Riess and his team argue, improved estimates of how fast the universe is expanding by 30 percent. And that appears to have ruled out a competing hypothesis that the acceleration is an illusion, caused by an hypothesized eight-billion-light-year "bubble" of empty space surrounding the Milky Way's galactic neighborhood.

"We are using the new camera on Hubble like a policeman's radar gun to catch the universe speeding," Riess said. "It looks more like it's dark energy that's pressing the gas pedal."

The new results are reported in the April 1 edition of The Astrophysical Journal.

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