Dr. Mark Dickinson, of the National Optical Astronomy Observatory, Tucson, Ariz., and principal investigator for the new observations, said, "With these ultra-deep Spitzer images, we are easily seeing objects throughout time and space, out to redshifts of 6 or more, where the most distant known galaxies lie. Moreover, we see some objects that are completely invisible, but whose existence was hinted at by previous observations from the Chandra and Hubble Observatories."
Seven of the objects detected by Spitzer may be part of the long-sought population of "missing" supermassive black holes that powered the bright cores of the earliest active galaxies. The discovery completes a full accounting of all the X-ray sources seen in one of the deepest surveys of the universe ever taken.
This detective story required the combined power of NASA's three orbiting Great Observatories — the Hubble Space Telescope, Chandra X-ray Observatory, and Spitzer Space Telescope. Each observatory works with different wavelengths of electromagnetic radiation, from high-energy X-rays with Chandra, through visible light with Hubble, and into the infrared with Spitzer. Together, these telescopes yield far more information than any single instrument.
All three telescopes peered out to distances of up to 13 billion light-years toward a small patch of the southern sky containing more than 10,000 galaxies, in a coordinated project called the Great Observatories Origins Deep Survey (GOODS). Chandra images detected more than 200 hundred X-ray sources believed to be supermassive black holes in the centers of young galaxies. The X-rays are produced by extremely hot interstellar gases falling into the black holes.
Hubble's Advanced Camera for surveys revealed optical galaxies around almost all the X-ray black holes. However, there remained seven mysterious X-ray sources for which there was no optical galaxy. Dr. Anton Koekemoer of the Space Telescope Science Institute, Baltimore, Md., who discovered these sources, presented three intriguing possibilities for their origin.