Left: Composite image of galaxy cluster Abell 85, using X-ray data (purple) from Chandra and optical image from the Sloan Digistal Sky Survey. Right: Snapshots of the Universe's evolution from a simulation by Volker Springel of MPA, at 0.9, 3.2 and 13.7 billion years.

A cross-continental team of astronomers led by Andrei Vikhlinin have used data from the American X-ray space telescope Chandra to help pin down the nature of the most enigmatic stuff in the Universe, dark energy. By observing clusters of galaxies over a range of different ages, the team were able to track how their masses have evolved over the history of the Universe. Using the statistics of this evolution and comparing them with results from several other complimentary studies, they have significantly narrowed the constraints on the precise nature of dark energy.

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