720 XTF Search Results (expand=spectral-Type;f1-spectral-Type=Optical;f2-associated-Lesson=Gamma Ray History);f1-spectral-Type%3DOptical;f2-associated-Lesson%3DGamma%20Ray%20History Results for your query: expand=spectral-Type;f1-spectral-Type=Optical;f2-associated-Lesson=Gamma Ray History Thu, 01 Jan 1970 12:00:00 GMT Hubble Stays on Trail of Fading Gamma-Ray Burst Fireball, Results Point to Extragalactic Origin. It is difficult to determine the origin of a GRB, but sometimes it can be done. The visible light of this GRB was detected by ground-based telescopes, and once the light had faded a deep picture by the Hubble showed this GRB was located in a faint distant galaxy Fri, 05 Sep 1997 12:00:00 GMT