The Gamma-Ray Sky

This view from NASA's Fermi Gamma-ray Space Telescope is the deepest and best-resolved portrait of the gamma-ray sky to date. The image shows how the sky appears at energies more than 150 million times greater than that of visible light. Among the signatures of bright pulsars and active galaxies is something familiar -- a faint path traced by the sun. Credit: NASA/DOE/Fermi LAT Collaboration

Update: Wednesday, October 28, 2009, Fermi Telescope Caps First Year With Glimpse of Space-Time
This view of the gamma-ray sky constructed from one year of Fermi LAT observations is the best view of the extreme universe to date. Credit: NASA/DOE/Fermi LAT Collaboration
In this illustration, one photon (purple) carries a million times the energy of another (yellow). Some theorists predict travel delays for higher-energy photons, which interact more strongly with the proposed frothy nature of space-time. Yet Fermi data on two photons from a gamma-ray burst fail to show this effect, eliminating some approaches to a new theory of gravity. The animation link below shows the delay scientists had expected to observe. Credit: NASA/Sonoma State University/Aurore Simonnet