New South Pole telescope to help explain why universe is accelerating
A multi-institutional team of scientists led by the University of
Chicago will receive $16.6 million from the National Science
Foundation over the next five years to build a telescope at the South
Pole aimed at piercing one of the darkest secrets of the universe.
The telescope will help scientists to reveal new details
regarding a mysterious phenomenon called dark energy, which makes the
expansion of the universe accelerate. Albert Einstein’s famous
“cosmological constant,” which is one possibility for the dark
energy, also will come under the telescope’s scrutiny.
The “gravity” of dark energy is repulsive. It pushes the universe
apart and overwhelms ordinary gravity, the attractive force exerted
by all matter in the universe. Dark energy is invisible, but
astronomers will be able to see its influence on clusters of galaxies
that formed within the last few billion years.
“With the South Pole Telescope we can look at when galaxy
clusters formed and how they formed. That is critically dependent on
the nature of the dark energy, this elusive component of the
universe,” said the University of Chicago’s John Carlstrom, who heads
the project. “We’ve only known about dark energy for a few years. No
one really knows what it is.”
Carlstrom’s partners in the project are Stephan Meyer, Clem
Pryke and Erik Leitch, University Chicago; Joe Mohr, University of
Illinois, Urbana-Champaign; Bill Holzapfel and Adrian Lee, University
of California, Berkeley; John Ruhl, Case Western Reserve University;
and Tony Stark, Harvard-Smithsonian Center for Astrophysics. Also
contributing to the project are Wayne Hu and Andrey Kravtsov of the
University of Chicago’s Center for Cosmological Physics, which
provided seed funding for the project.
“One of our main goals is to figure out what the dark energy
is,” said center Director Bruce Winstein, the University’s Samuel K.
Allison Distinguished Service Professor in Physics. “Is it a
cosmological constant or is it dynamical? The South Pole Telescope
holds the promise to give us a lot of new, valuable information on
this.”
Understanding dark energy is one of the key scientific
questions called out in the Astronomical Decadal Survey. In the
survey, astronomers identified a South Pole telescope as one of their
highest-priority projects for the next 10 years. “It’s a way of
taking the next step in understanding this crazy new cosmology that
we find ourselves in,” said astronomer Tony Stark of the
Harvard-Smithsonian Center for Astrophysics.
The telescope will measure eight meters (26.4 feet) in
diameter and will operate at submillimeter
wavelengths, between microwaves and the infrared on the
electromagnetic spectrum. The Berkeley scientists will lead the
effort to construct the telescope’s array of 1,000 bolometers (heat
detectors). “This will be the largest bolometric array yet built,”
said Carlstrom, the S. Chandrasekhar Distinguished Service Professor
at Chicago.
The bolometers are sensitive enough to measure temperature
differences in the sky with an accuracy of 10 millionths of a degree.
The background temperature of the universe is so cold-hundreds of
degrees below zero-that even ice is hot by comparison.
The telescope will be located at the National Science
Foundation’s South Pole Station, to take advantage of Antarctica’s
clear, dry skies. “Although a forbidding environment, scientists,
with support from the NSF’s Office of Polar Programs, have
demonstrated in recent years that they can mount sophisticated
experiments and produce astonishing results,” said Michael Turner,
the University of Chicago’s Bruce and Diana Rauner Distinguished
Service Professor in Astronomy & Astrophysics.
The new telescope is scheduled to become operational in four
years. Its first key science project will be to search one-tenth of
the sky for the Sunyaev-Zel’dovich effect in galaxy clusters. The S-Z
effect is created when the cosmic microwave background radiation (the
afterglow of the big bang), passes through the gas contained within
galaxy clusters. As the microwaves interact with the gas in the
clusters, some of the microwaves change in frequency. The South Pole
Telescope will measure the slight temperature difference associated
with the frequency change and produce an image of the gas in the
cluster.
The South Pole Telescope team also will use the S-Z effect to
search for and count as many as 10,000 clusters of galaxies.
Carlstrom and his colleagues will look at how galaxy clusters
have formed and evolved over the last few billion years. This is
relatively recent in the history of the 14-billion-year-old universe.
By the end of the telescope’s first year of operation,
scientists expect to be able to confirm or disprove the validity of
Einstein’s cosmological constant. If Einstein’s idea is correct, the
South Pole Telescope team will find that dark energy was a less
influential force in the universe 5 billion years ago than it is
today.
The South Pole Telescope will complement another project also
led by Carlstrom, the S-Z Array, which is under con
Image available at
http://www-news.uchicago.edu/releases/photos/spt/
