Another clue in the case for dark matter

DENVER — Using a sensitive detector to survey the abundance of high-energy electrons and positrons in nearby reaches of space, the Fermi Gamma-ray Space Telescope has found new evidence that may hint at the existence of dark matter, the exotic invisible material believed to make up 85 percent of the mass of the universe.

The measurements, reported May 2 at a meeting of the American Physical Society and also online May 4 in Physical Review Letters, bolster the possibility that another orbiting observatory called PAMELA (for Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) did indeed see indirect signs of dark matter (SN: 9/27/08, p. 8), which has eluded detection ever since astronomers first proposed the material more than 75 years ago.

But it’s also possible that many of the energetic electrons and positrons Fermi recorded might instead