Director's Report: HETDEX Progress Update
David Lambert, Director, McDonald Observatory
The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is taking shape. Team members at universities in Texas and Germany are working to create the hardware and computer programs that will enable our look back at the expansion history of the Universe, to provide unique data for solving the riddle of dark energy.
Dark energy dominates the Universe. It constitutes about 73 percent of the cosmos, while everything made of atoms accounts for a mere four percent, and the rest — about 23 percent — is made up of a mysterious “dark matter.” Dark energy’s effects have been reconfirmed by numerous observations: It is causing the Universe to expand at an accelerating rate (when the expansion should be slowing down). Beyond that fact and a rough approximation of the amount of energy needed to account for the observed effects, nothing is known.
The importance of dark energy to our understanding of the Universe was highlighted by the 2011 Nobel Prize in Physics, which was awarded to two teams that made the discovery of the Universe’s accelerating expansion. We are proud that, with HETDEX, our Texas astronomers are leading the effort to go beyond discovery to a physical understanding of dark energy.
The first phase of creating HETDEX was to design and build a new tracker assembly for the Hobby-Eberly Telescope. The upgraded wide-field corrector and prime focus instrument package needed for HETDEX have larger mirrors than those currently housed at the HET’s prime focus. Together, they are seven times heavier than the current package, and they require a new, stronger tracker structure. New gears and motors have been designed for HETDEX that will move the parts of the 3.4-ton prime focus instrument package around 10 different axes with a precision of plus or minus .002 millimeters.
The new tracker built for HETDEX undergoing testing at the Center for Electromechanics in Austin
That complex new tracker assembly and much of the new prime focus instrument package are operational and are undergoing testing at The University of Texas at Austin’s Center for Electromechanics.
The second phase of creating HETDEX is the design and construction of a suite of 150 innovative integral-field spectrographs (arranged in 75 pairs), collectively called VIRUS. Teams in Potsdam, Germany, and at UT Austin and Texas A&M are building the components and beginning the assembly of the first set of VIRUS spectrographs, which will be integrated and tested at Texas A&M. Current planning calls for installation of VIRUS beginning in mid 2012.
We plan to take the Hobby-Eberly Telescope offline in March 2012 and to begin installing the new tracker in April. The pacing item for installation will be delivery of the new wide-field corrector mirror from the University of Arizona’s College of Optical Sciences, now slated for early 2012.
We then plan to begin HETDEX observations in September 2012 with 32 pairs of VIRUS spectrographs and with the full complement of 75 pairs by year’s end.
HETDEX can show better than any competing project whether dark energy has evolved over time, which is critical to unlocking dark energy’s secrets. HETDEX will also determine whether, to a few tenths of a percent, the Universe’s geometry is curved or flat, a measurement that our competitors will need to test the validity of their dark-energy observations in more recent times.
As exciting as HETDEX is, I am just as energized by the new capabilities that the HETDEX upgrades and VIRUS spectrographs will give to all other observations with the HET. These new capabilities will open up whole new areas in astrophysics for studies of galaxy formation, the large-scale structure of the Universe, the characteristics of dark matter in nearby galaxies, and the history of our own Milky Way, and the HET will be unrivaled for these new areas of exploration.
HETDEX has received wonderful support from the State of Texas and The University of Texas at Austin, from U.S. government agencies, from our partner institutions, and from generous private donors.
In early 2012, we will set a date for the dedication of HETDEX and a ceremony to recognize our generous donors. A highlight of that ceremony will be naming the new tracker assembly and wide-field corrector “The Harold C. Simmons Dark Energy Optical System,” in honor of the generous benefactor whose leadership has done so much to make HETDEX possible.
I look forward to celebrating with you in 2012, and I invite you to explore more about dark energy and HETDEX at the HETDEX team's Web site:
HETDEX Illuminating the Darkness
[David L. Lambert]