File:Chandra Deep Field-North without outlines (2001-cdfn-more-3).jpg

English: Chandra Deep Field-North without outlines Shown is an extremely deep Chandra X-ray Observatory image of the Hubble Deep Field-North (HDF-N), the most intensively studied patch of the night sky at all wavelengths from radio to X-ray. This image is thus the best combination of the deepest imaging capabilities available in both the optical and X-ray regimes. Twelve X-ray sources are detected in the HDF-N. The false colors represent the "X-ray color" of the objects. Objects that appear redder are cooler in the X-ray band, while objects which are more blue are hotter in the X-ray band. About half of the sources show strong evidence that the X-rays are due to accretion onto supermassive black holes. The other sources have much lower luminosities, and in several cases are fairly nearby. In these galaxies, the Chandra X-ray detection is most likely the summed emission from a handful (or even one) bright sources within the galaxy, such as stellar-size black holes in binary star systems, the hot gas within the galaxy, or the remnants of supernova explosions. Chandra is thus now peering far enough into the universe to detect the type of X-ray emission that one finds in "normal" galaxies such as the Milky Way. This allows us to look back several billion years to see what our own galaxy and neighborhood (the Local Group) might have been like at earlier times. Chandra ACIS image