Known as RCW 38, a star cluster covers a region about 5 light years across. It contains thousands of stars formed less than a million years ago and appears to be forming new stars even today. The crowded environment of a star cluster is thought to be conducive to the production of hot gas, but not high-energy particles. Such particles are typically produced by exploding stars, or in the strong magnetic fields around neutron stars or black holes, none of which is evident in RCW 38. “The RCW 38 observation doesn’t agree with the conventional picture,” said Scott Wolk of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., lead author of an Astrophysical Journal Letters paper describing the Chandra observation. “The data show that somehow extremely high-energy electrons are being produced there, although it is not clear how.” Other authors of the paper, which appeared in the Dec. 1, 2002 issue of the Astrophysical Journal Letters, were Tyler Bourke, Randall Smith and Bradley Spitzbart of the Harvard-Smithsonian Center for Astrophysics, and Joao Alves of the European Southern Observatory in Garching, Germany.