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The Chandra space observatory has revealed that an enigmatic star cluster 6000 light years from Earth is immersed in a mysterious cloud of high-energy electrons.

The cluster of stars, designated RCW 38, has an X-ray spectrum indicating that its surrounding gas cloud is filled with extremely high-energy electrons moving through a magnetic field. These high-energy particles are normally associated with supernova explosions or the neutron stars they leave behind, but not star clusters.

“The RCW 38 observation doesn’t agree with the conventional picture,” says Scott Wolk of the Harvard-Smithsonian Center for Astrophysics, who led the team that imaged the cluster.

Wolk’s team, and colleagues at the European Southern Observatory in Germany, speculate that a supernova may have faded thousands of years ago leaving behind an undetected neutron star that is responsible for the observed X-rays.

Radiation beam

A neutron star emits a beam of radiation that would accelerate the cluster’s electrons enough to cause the high-energy X-ray emissions. But this beam might also be spinning in a way that means it cannot be observed directly from Earth – think of looking down on a lighthouse from an airplane.

Martin Barstow, at Leicester University in the UK, agrees with the theory. “It sounds like a good explanation to me,” he told Â鶹´«Ã½. “The kind of radiation that they are quoting seems to be fairly typical of something like the crab nebula, and we know this is powered by a central neutron star.”

The young, hot stars within the cluster will form discs that should eventually form orbiting planets. Wolk adds that the high-energy electrons would have a significant effect on the formation of such disks: “Regardless of the origin of the energetic electrons, their presence would change the chemistry of proto-stellar disks in ways that could still be manifest billions of years later.”

Journal reference: Astrophysical Journal Letters (vol 582)