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Breaking ground on exploring the universe

The Kavli Institute for Particle Astrophysics and Cosmology (KIPAC)

An artist's rendition of the planned Fred Kavli Building at the Stanford Linear Accelerator Center.

BY HEATHER ROCK WOODS

The Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) broke ground June 28 for the new Fred Kavli Building at the Stanford Linear Accelerator Center. Researchers at the institute, which kicked off its science program last summer, are looking to unravel fundamental mysteries that connect the tiniest particles and universe-shaping forces. "Our programs range from physics that happens in the very early universe to the physical processes of current sources like black holes, both from a theoretical and experimental standpoint," said Steve Kahn, deputy director of KIPAC.

The institute has joined three experiments that seek to find and explain dark matter and dark energy, the shadowy constituents of 96 percent of our universe. The answers lie in better observations of the universe and in higher-energy accelerators on Earth.

"Very exciting discoveries in the last 10 years have changed our understanding of the universe and shown deep connections to high energy physics," Kahn said.

KIPAC is taking the lead in designing and building a camera for a proposed ground-based telescope that will survey the entire visible sky every few nights to observe even faint objects. Called the Large Synoptic Survey Telescope (LSST), it will work more rapidly, be 20 times more powerful than existing survey telescopes and "produce a great map of all the dark matter in the universe," Kahn said.

To capture and record images every 10 seconds, the telescope will use the biggest digital camera ever built at six feet tall and a few thousand pounds. Kahn is leading the development of the camera, which will have 2.8 billion pixels, 500 times more than a typical consumer digital camera. LSST is envisioned to be a joint National Science Foundation and Department of Energy (DOE) project with many collaborating institutions and public and private funding.

To map dark matter, scientists look for the effects it creates, somewhat like studying animal tracks to learn about elusive animals. The gravitational pull of dark matter bends light streaming from distant galaxies toward Earth. LSST will observe these distortions, called weak gravitational lensing, to map the location of dark matter and, more importantly, how it's clustered together.

"This may be one of the best ways of analyzing the evolution of the universe," said KIPAC Director Roger Blandford. "It gives us useful information about the size and shape, growth and structure of the universe."

Detailed measurements of the distribution of dark matter will shine intellectual light on dark energy -- the perplexing 'anti-gravity' force that is driving the universe to expand at an accelerating rate.

"So the telescope will help us understand dark energy, using dark matter as a probe," Kahn said.

The telescope will become operational in 2012, several years after the start of a new accelerator at the European Organization for Nuclear Research (CERN) in Geneva that may find evidence for supersymmetry -- a current theory in particle physics to explain dark matter and to unify the fundamental forces.

Using supernovae to illuminate dark energy

KIPAC also has joined forces with other institutions in a joint NASA-DOE project aimed at measuring dark energy, but by using a different technique. KIPAC will develop and build the digital electronics for a proposed space-based telescope called the Joint Dark Energy Mission (JDEM). This project, led by Lawrence Berkeley National Laboratory, will more precisely gauge the age and acceleration of the universe.

The JDEM telescope will record supernovae that always create the same intrinsic brightness when they explode. Dimmer supernovae are farther away than brighter ones. Linking their distance with their redshift -- a measure of velocity based on how red, or stretched out, the light waves appear -- allows calculations of how quickly they have moved away from Earth, and how fast the universe is expanding.

This experiment is similar to the one that discovered dark energy six years ago, but will go deeper into space to see more supernovae farther out and to measure them more precisely.

"It can tell us exactly how dark energy is behaving," Kahn said. "Does it have constant energy or does its force evolve with time? There are no reliable theoretical predictions; it's such a mystery. But we need to quantify what's happening to have a hope of understanding."

Adding to the universe's photo album

A more challenging space experiment is the proposed Nuclear Spectroscopic Telescope Array (NuSTAR) to measure energetic "hard" X-rays emitted near black holes and by other astronomical processes.

NASA selected NuSTAR as one of five finalists for a "small explorer" flight into space; two will be selected this year for launch dates in 2007 and 2008. One of 10 partners on the project, KIPAC is developing novel telescope mirrors to focus the X-rays.

"It's the best way to get a survey of the black holes in the universe," Kahn said. "We'll make the first real X-ray pictures of the sky," filling in a blank spot in the photo album of the universe at various wavelengths: visible light, microwave, infrared and ultraviolet.

NuSTAR would also make simultaneous, complementary observations with the Gamma Ray Large Area Space Telescope (GLAST), an international project headed by Stanford physics Professor Peter Michelson that will take pictures at gamma ray wavelengths.

Working in the wavelength of "hard" X-rays, which are shorter and more energetic than "soft" X-rays, requires innovative focusing mirrors. The mirrors were invented by a team from Columbia University and Lawrence Livermore National Laboratory and are now being developed by KIPAC project scientist Bill Craig, an expert in X-ray optics. KIPAC scientists are also doing theoretical work for NuSTAR.