Gamma ray spectroscopy: <i><a href="https://en.wikipedia.org/wiki/Energetic_Gamma_Ray_Experiment_Telescope" class="extiw" title="en:Energetic Gamma Ray Experiment Telescope">EGRET</a> All-Sky Gamma Ray Survey above 100 MEv</i>. The bright line is the Milkyway
<a rel="nofollow" class="external autonumber" href="http://heasarc.gsfc.nasa.gov/docs/objects/heapow/archive/large_scale_structure/egret_allsky.html">[1]</a>