Scientific American - 2010 April 19
By retrofitting a Texas telescope with a low-cost, modular instrument, researchers hope to find clues to what is driving the accelerating expansion of our universe
An experiment is gearing up in Texas to take on one of the universe's biggest mysteries by compiling a three-dimensional map of the early cosmos. The hope is that the survey will help inform astronomers and cosmologists about the nature of dark energy, a mysterious and hypothetical agent thought to constitute nearly three quarters of the universe's mass.
Dark energy is the term used by cosmologists to explain why the expansion of the universe is accelerating rather than slowing due to gravitation. Yet the name only hints at how little we know about it. Is dark energy a particle, a wave or a fundamental property of space-time? Has it always been there? Is it constant, or does it grow stronger as the universe expands? Hypotheses abound, but there is scant observational evidence to back them up. After all, it was not until 1998 that studies of distant supernovae provided the first solid evidence for a universe undergoing accelerated expansion.
The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is one of three ambitious projects aiming to provide those missing observations. The others are the Baryon Oscillation Spectroscopic Survey (BOSS), which achieved first light in September 2009 at the 2.5-meter Apache Point telescope in New Mexico, and the Dark Energy Survey (DES), which will add a digital camera with more than 500 megapixels to the Blanco four-meter telescope in Chile.