Imagine the Universe!

Other Problems with Detecting High-Energy Gamma-Rays

In order to make a clear image, with lots of definition, you need to have many many photons. Imagine how poor a photograph would look if the picture was from only a few dots of light, instead of millions and millions. One of the things that makes high-energy gamma-ray observations difficult is the fact that just are not that many of these highest energy photons around. At the highest energies seen by EGRET, there may be only one photon that hits the detector in a whole year! In order to make a good observation, then, we have to wait a long time to collect all of the available photons. The All-Sky map below took 18 months to collect all of the data.

EGRET allsky image

Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Acting Project Leader: Dr. Barbara Mattson
All material on this site has been created and updated between 1997-2012.

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