Expansion of the Universe Was Once Thought Sluggish – Now Speeding up

Exploding stars, called Supernovae, that are
three-quarters of the way across the universe have helped astrophysicists
discover that the universe has expanded at different rates over its cosmic
history, reports Adam Riess from the Space Telescope Science Institute in
Baltimore and a member of the Hubble Higher-z Supernova Search Team. He
announced Friday, October 10, during the first-day of the Kavli-CERCA
Future of Cosmology conference at Case Western Reserve University that
approximately five billion years ago the universe began to accelerate in
its expansion.

These new findings derived from images captured by the Hubble
Space Telescope. Riess was among 70 of the world’s leading researchers at
the Kavli-CERCA (Center for Education and Research in Cosmology and
Astrophysics) Future of Cosmology conference to explore the science of the
universe, to report new information and to discuss the next 25 years of
research.

“These Supernovae confirm past cosmic slowdown and the reality of
recent cosmic acceleration or dark energy,” states Riess.

“With Supernovae, we have mapped the preceding 75 percent of the
expansion history of the universe,” reported Riess.

Using the Hubble Space Telescope, the research group found six of
the seven most distant Supernovae known and beyond the transition point
between its slowdown and acceleration.

The Hubble Higher-z Supernova Search Team looked at a particular
class of Supernovae known as Type 1a that are bright enough at ~10 billion
solar luminosities at their peak light to be seen halfway across the
visible universe from the ground and even further back in time with the
Hubble Space Telescope.

While the previous slowdown was predicted by theory, Riess says
actually seeing it “represents a crucial test of the new cosmological
paradigm, which is now well-confirmed.”

Five years ago, Riess and the High-z Supernova Search Team
reported findings that the universe was speeding up in its expansion, which
ran counter to what was expectednamely that the attractive gravity of dark
matter would slow the expansion of the universe.

He further explains that gaining favor over the past years is the
theoretical explanation that the universe is also filled with a repulsive
dark energy.

Others on the Hubble Higher-z Supernova Search Team, under the
direction of Riess, are Lou Strogler, Peter Challis, John Tonry, Stefano
Casertano, Alex Filippenko, Robert Kishner, Widong Li, Saurabh Jha, Chuck
Steidel, Mark Dickenson and the Goods Team under the direction of Mauro
Giavalisco.

CERCA is a new center, designed to enhance the world-class
research programs in cosmology and astrophysics already at Case by
providing fellowships to enable some of the world’s best young researchers
to spend time at the University. The new center will come under the
direction of Lawrence Krauss, Case chair and Ambrose Swasey Professor of
Physics and the author of the best-selling book, The Physics of Star Trek.
CERCA will involve a partnership between Case and its University Circle
neighbor, the Shafran Planetarium at the Cleveland Museum of History, to
design popular planetarium programs and ultimately documentaries and films
that inform the general public about the latest developments in cosmology
and astrophysics, says Krauss, adding that programs developed for the
Shafran Planetarium eventually could be used by other planetariums around
the country.

Contact: Adam Riess at 410-790-9435 or at ariess@stsci.edu

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