Astronomers have long wondered where the mysterious x-ray glow in the Milky Way plane comes from. Now new evidence, described in the current issue of the journal Science, may help to settle the matter. According to the report, researchers using NASA's Chandra X-Ray Observatory have traced the emission to a hot, diffuse gas.

Ken Ebisawa of the NASA Goddard Space Flight Center and his colleagues focused on a small sector of the galactic plane in the constellation Scutum. Probing what is known as the zone of avoidancea region of space so-named because no optical observations have been made of itChandra detected a diffuse emission, as opposed to x-ray point sources. This, the researchers explain, indicates the x-ray glow comes from tremendously hot plasma gas concentrated along the galactic plane.

The team also detected 36 new distant x-ray point sources beyond the plane. These, they believe, are active galaxies located millions of light-years behind our own.