A Johns Hopkins astrophysicist is principal
investigator of a proposal, accepted last week by NASA, to
design a space mission to determine the properties of the
mysterious dark energy that is causing the expansion rate
of the universe to speed up.
Called the Advanced Dark Energy Physics Telescope, the
mission promises to determine the location of 100 million
galaxies. It would be the most comprehensive survey of the
universe ever undertaken, according to Charles L. Bennett,
professor in the Henry
A. Rowland Department of Physics and Astronomy at the
Krieger School of Arts and Sciences. In addition, ADEPT
promises to discover about 1,000 new supernovae.
"We are delighted the reviewers recognized that the
ADEPT approach is important and very powerful," Bennett
said. "It is based on experimental breakthroughs that have
occurred in just the last three years. The reviewers also
recognized that the mission is practical and that we have a
top-notch and highly experienced team. We believe that
ADEPT's results are likely to be of extraordinary
importance to science."
"Dark energy" is the term used to describe a new form
of energy that is thought to permeate all of space. Unlike
ordinary gravity, which consists of an "attractive," or
inward-pulling, force, dark energy is "repulsive," or
outward-pushing. Cosmologists know that something is
driving an accelerated expansion of the universe and is
acting like an anti-gravity force. Because this energy has
never been directly seen and its identity is as yet
unknown, it is called dark energy.
"Is the physical nature of dark energy constant, or
does it evolve with time? To answer this question, we must
look back in time, and for astronomers, that means looking
at distant objects," Bennett said.
The original discovery of dark energy came from
observing a special kind of exploding star, or supernova.
Adam Riess, also a professor of physics and astronomy at
Johns Hopkins and a member of the ADEPT team, first
discovered dark energy in this way with his colleagues.
"ADEPT will measure these supernovae, but its real
advance lies in a new, more powerful technique. Patterns in
temperature of the very young universe provide a standard
ruler that is imprinted on the pattern of galaxies across
the sky. ADEPT aims to map these through space and time,"
according to Bennett.
ADEPT promises to provide the galaxy positions needed
to follow the historical development of the universe so
that astronomers can determine the role played by the dark
energy. Bennett says that the ADEPT mission will help
answer many questions about the role played by dark energy
in both fundamental physics and cosmology.
Jonathan Bagger, chair of the Johns Hopkins Physics
and Astronomy Department, agreed. "Twenty-first century
physics is at a crossroads," he said. "Our fundamental
theories of gravity and quantum mechanics are in conflict.
Dark energy might point the way out."
Adam Falk, dean of Arts and Sciences, said, "The
Krieger School of Arts and Sciences has a long and proud
history of space science accomplishments. We look forward
to addressing one of the most important scientific problems
of our day."
The NASA Goddard Space Flight Center in Greenbelt,
Md., with its science and engineering expertise, will be
Johns Hopkins' partner on ADEPT.
Bennett has extensive experience as a principal
investigator. He leads the Wilkinson Microwave Anisotropy
Probe, a highly successful NASA space mission that has been
determining precisely the age, composition and curvature of
the universe. WMAP measures the temperature of cosmic
background radiation, the oldest light in the universe. In
March, Bennett and his team made international news with
their announcement that the universe bears signs that it
expanded from quantum fluctuations to astronomical scales
within its first trillionth of a second. The finding, based
on data from WMAP, supports a 20-year-old theory known as
"inflation" that describes how the cosmos grew from
subatomic in size to a vast expanse of stars and galaxies
over 13.7 billion years.
Other science-team institutions that will be involved
in the project are the University of Hawaii, Princeton
University and the Institute for Advanced Study, the
Space Telescope Science
Institute, the University of Arizona, the University of
British Columbia and the University of Pennsylvania.
Lockheed-Martin and ITT are industrial partners.
GO TO