Chandra Advanced Charged Coupled Imaging Spectrometer (ACIS) image (contours) and optical image (color pixels) of a newly discovered powerful X-ray source in a distant galaxy. Photo: X-ray: NASA/CXC/SAO Optical: ESO/La Silla

NASA's Chandra X-ray Observatory has discovered an unusually strong source of X-rays -- a possible hidden black hole -- in a galaxy 2.5 billion light years from Earth.

When viewed with an optical telescope, this galaxy appears normal. But when the Chandra X-ray Observatory observed the galaxy during calibration testing in September 1999, it discovered an unusually strong source of X-rays.

Located 2.5 billion light years from Earth, the X-ray source is concentrated in the central regions of the galaxy and could be another example of a veiled black hole. This discovery adds to a growing body of evidence that our census of energetic black hole sources in galaxies is far from complete.

A team of Italian and Harvard-Smithsonian scientists, led by Fabrizio Fiore of the Astronomical Observatory of Rome, and the Harvard-Smithsonian Center for Astrophysics, made the discovery. The vertical lines in the image are part of a grid to locate the source in the sky. The X-ray contours are consistent with a point-like source in the center of the galaxy. The colors in the optical image represent brightness levels. The source name is CXOUJ031238.9-765134, which defines its position in the sky.

NASA's Chandra X-ray Observatory was launched into space in July aboard the space shuttle Columbia. Chandra is the space agency's third "Great Observatory" launched, joining the Hubble Space Telescope and Compton Gamma Ray Observatory.