June 18, 2004  




The KIPAC Guide to Exploring the Universe

By Heather Rock Woods

Scientific forecast: heavy dark matter and gusty dark energy with a chance of exciting discoveries.

KIPAC is leading the effort to design and build the LSST camera which will be the world’s biggest digital camera. (Courtesy of Steve Kahn)

The young Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) has already kicked off its science program, looking to unravel fundamental mysteries that connect the tiniest particles and universeshaping 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’s inaugural experiments (see TIP, January 23, 2004) 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.

Land-Based Telescope with Powerful Sight

One project is a 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 works more rapidly, is 20 times more powerful than existing survey telescopes and will “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. KIPAC is taking the lead in designing and building the camera, that will have 2.8 billion pixels (500 times more than in a typical consumer digital camera). LSST is envisioned to be a joint NSF and DOE project.

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 ma� er 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. It gives us useful information about the size and shape, growth and structure of the universe,” said Roger Blandford, KIPAC director.

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,” said Kahn. The telescope comes online in 2012, several years after the start of a new accelerator at CERN that may find evidence for supersymmetry— particle physics’ current theory to explain dark matter and to unify the fundamental forces.

Using Supernovae to Illuminate Dark Energy

The second main project is also aimed at measuring dark energy but by a different technique. KIPAC will develop and build the electronics for a space-based telescope called the Joint Dark Energy Mission (JDEM).

This joint NASA and DOE project 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 on 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. 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,” Kahn said.

Adding to the Universe’s Photo Album

A more challenging space experiment is NASA’s provisionally accepted NuSTAR to measure energetic hard x-rays emitted near black holes and by other astronomical processes.

"It’s the best way to get a survey of the black holes in the universe,” said Kahn. “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. The GLAST project at SLAC is already working on taking pictures at gamma ray wavelengths.

Working in the hard x-ray wavelength band requires novel telescope mirrors to focus the x-rays. The mirrors were invented by a team from Columbia University and LLNL and are now being developed by project scientist Bill Craig (KIPAC), an expert in x-ray optics. In addition KIPAC is doing theoretical work for NuSTAR.

The Institute’s Other Half

The other half of KIPAC involves theoretical and observational work. KIPAC professors, scientists, postdocs and students are evaluating and working on theories about the nature of dark matter and dark energy, relativistic astrophysics for black holes, high-energy cosmic rays and neutron stars, and the source of gamma ray bursts.

“We have very good projects,” Blandford said. “We’re not sure where the future will take us because it’s a rapidly moving field. We’re hopeful we can develop strong and productive research here.”


The Stanford Linear Accelerator Center is managed by Stanford University for the US Department of Energy

Last update Wednesday June 16, 2004 by Emily Ball