APL Colloquium

January 27, 2012

Colloquium Topic: Dark Energy and The Cosmic Expansion History

The expansion rate and its evolution must be empirically determined for our Universe to reveal its composition, scale, age, and fate. The Hubble Space Telescope is unique in its ability to measure the keystones of cosmic expansion, distant Type Ia supernovae and Cepheid variables in their hosts. In 1998, high-redshift Type Ia supernovae provided the first and only direct evidence for an accelerating Universe and the existence of dark energy. Presently, refinements in these measurements and new techniques have begun to narrow the range of properties and explanations for the nature of dark energy. I will review a number of these recent experiments including improvements in the determination of the Hubble constant using a new infrared array on the Hubble Space Telescope and a 3 year search for the most distant exploding stars, perhaps among the very first supernovae in the Universe.

Colloquium Speaker: Adam Riess

Dr. Adam Riess is a co-recipient of the Nobel Prize in Physics 2011 "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae."

Adam Riess is a Professor of Physics and Astronomy at Johns Hopkins University and on the Staff of the Space Telescope Science Institute. He leads the Higher-Z SN Search program, which uses the Hubble Space Telescope to discover distant supernovae. This program has studied the expansion of the universe over 10 billion years ago.  This work has detected an early phase of decelerating expansion, causing the most distant supernovae to look relatively brighter. This tends to confirm the dark energy - dark matter model.

 In 1998, as a Miller Fellow at the University of California at Berkeley he led the study for the High-Z Supernova Search Team which first reported evidence that the universe's expansion rate is accelerating. This result was also found by the Supernova Cosmology Project. Science Magazine named the discovery of the accelerating universe the 1998 "Breakthrough of the Year."

 In 1999, Adam Riess  received the Trumpler Award from the Astronomical Society of the Pacific. He received the Bok Prize from Harvard University in 2001, the Helen B. Warner Prize in 2003 from the AAS and the Raymond and Beverly Sackler Prize in 2004.  In 2006, he received the Shaw Prize in Astronomy for the discovery of cosmic acceleration and shared the 2007 Gruber Prize with members of the High-Z team and the Supernova Cosmology Project. Riess was awarded a MacArthur Fellowship in 2008, elected to the National Academy of Sciences in 2009 and was a recipient of the Einstein Medal in 2011.  He received his bachelor's degree from MIT in 1992 in Course 8 and his Ph.D. from Harvard in 1996.