Page 3/3 - Posted April 1, 2011
Spreading out at Pole
Make that BICEP2.
The first BICEP experiment ran from 2006-08. It didn’t detect B-mode polarization but it significantly narrowed the search. Cosmologists believe there is an indirect upper limit for how bright the polarization signal from inflation might be. The goal is to get below that upper limit and determine how faint that signal could be.
“With BICEP2 we’re hoping to make the next best direct constraint — or detect B mode polarization,” Brevik said.
The second-generation BICEP telescope made some technological leaps in hardware that allow it to map the sky about 10 times faster than its predecessor did. “In four days, we roughly achieved the same sensitivity map that BICEP1 would make in 40 days,” Brevik noted.
The SPUD telescope and its three receivers, housed in the nearby Martin A. Pomerantz Observatory on the old DASI telescope mount, are similar in ability to BICEP2. Next year the plan is to add two more receivers to the array.
Even that’s not enough “eyes” on the sky.
Chao-Lin Kuo at Stanford University envisions an even bigger array. He’ll start with Polar-1, a larger telescope than SPUD or BICEP that will be deployed in two years at the South Pole. Its “beam” will be smaller but with the higher resolution that comes with a bigger telescope.
“We want to have clearer maps with less noise, essentially,” Kuo explained over dinner in the South Pole dining room. “We’re going to improve sensitivity and resolution.”
Polar-1 will also join the search for CMB-generated B-mode polarization. But it will move beyond the quest for evidence of inflation to study some of the large-scale structures of the universe between the CMB and Earth using a technique called gravitational lensing.
Astronomers can measure how gravity bends the light of distant objects and calculate the gravitational pull of invisible matter. Gravitational lensing is another way to gain insight into persisting mysteries like dark energy and even neutrinos, subatomic particles with almost no mass produced by high-energy events in the universe.
“You’re using CMB as a tool to study matter distribution,” said Kuo, who is also a collaborator on the SPUD and BICEP programs. “We want to look at mass more directly, so gravitational lensing is one way to do it.”
Kuo said he hopes that Polar-1 lives up to its name, as the first of an array of CMB telescopes spread across the Dark Sector. The first generation will replace BICEP2 at the Dark Sector Lab.
“We eventually need multiple telescopes to get the sensitivity that we want or the survey speed that we want,” Kuo said. “We want Polar-1 to be a pathfinder for that program.”
The South Pole Telescope, currently focused on searching out galaxy clusters in the universe, will also shift to B-mode detection with the addition of a polarization-sensitive receiver in 2012.
Kovac said no one really knew where CMB research at the South Pole was going more than 15 years ago when he wintered with the Python telescope. “We only knew it was an exciting ride, and it hasn’t slowed down since then.”
NSF-funded research in this story: John Kovac, Harvard University, Award No.1044978 \; Clement L. Pryke, University of Minnesota-Twin Cities, Award No. 1110087 ; Chao-Lin Kuo, Sarah Church, James Bock and John Kovac, Stanford University, Award No. 0960243 . Background resources for this article included: “CMB from the South Pole: Past, Present and Future” by J.M. Kovac and D. Barkats, California Institute of Technology, Department of Physics; and “Alpha & Omega: The Search for the Beginning and the End of the Universe By Charles Seife (Penguin Books 2004).Back 1 2 3