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Dark Energy Survey

The DES begins five-year mission

Munich, 09/04/2013

From now on, the world's most powerful digital camera will turn its lenses skyward: Over the next five years, the 570-megapixel camera at the heart of the Dark Energy Survey will provide color images of one-eighth of the sky with unprecedented resolution. An international team of physicists and astronomers, including members of the Universe Excellence Cluster, will use this remarkable instrument to ascertain why the Universe is expanding ever more rapidly. Working from an observatory in Chile, their aim is to solve the mystery of “dark energy”, the force which is believed to be causing cosmological acceleration.

Aufnahme der Galaxie NGC 0895, etwa 110 Millionen Lichtjahre entfernt von der Erde. („Aufnahme der Galaxie NGC 0895, etwa 110 Millionen Lichtjahre entfernt von der Erde. (Foto: Dark Energy Survey)
Photo: Dark Energy Survey

In 1998, two teams of astronomers studying distant supernovae discovered that the rate of expansion of the Universe is progressively increasing. This finding is at variance with the theory of General Relativity. According to Einstein, gravity should lead to a slowing of cosmic expansion. To explain the observations, cosmologists have invoked a new form of energy which accounts for about three-quarters of the matter and energy in the Universe: Dark energy is assumed to exert a repulsive force on ordinary matter, which counteracts the effects of gravitational attraction. Alternative explanations for cosmic acceleration would require the replacement of General Relativity by a new theory of gravitation on cosmic scales.

The Dark Energy Survey (DES) is an international venture designed to determine why the Universe is expanding at an ever increasing rate. One of its founding members is Prof. Dr. Joseph Mohr, an astrophysicist on the Faculty of Physics at LMU Munich. The Survey’s goal is twofold - to find out why the expansion of the Universe is speeding up instead of slowing down, and to throw light on the mystery of dark energy, which is believed to be driving the acceleration. The Survey’s central tool is the Dark Energy Camera (DEC), a 570-megapixel digital camera, mounted on a telescope at the Cerro Tololo Inter-American Observatory in the Chilean Andes. This instrument includes five precisely shaped lenses, the largest nearly a meter in diameter. After ten years of planning, construction and testing, the Dark Energy Survey officially got underway on 31 August 2013. During the coming five years, a team of 120 physicists and astronomers will use the DEC to systematically map one-eighth of the sky. The Universe Excellence Cluster has been part of the collaboration since 2010. "The observations made by the Dark Energy Camera will tell us more about the fundamental nature of matter, energy, space and time," says astrophysicist Prof. Dr. Jochen Weller from the Faculty of Physics at LMU. Like his colleague Prof. Mohr, Weller is a Principal Investigator of the Universe Excellence Cluster and a member of the DES Consortium.

The DEC is the most powerful instrument of its kind. Each snapshot will record the light from more than 100,000 galaxies, out to a distance of eight billion light years. The Survey’s observations will not be able to determine the nature of dark energy directly. However, the data acquired by the Survey will provide insights into the expansion of the Universe and the growth of large-scale structures over time, and enable scientists to define the properties of dark energy with greater precision than ever before.

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