[Music throughout](Announcer): Liftoff of the Delta rocket carrying a gamma-ray telescope searching for unseen....[fades out] (Narrator): I'm Julie Mcenery, Fermi project scientist. Since its launch in 2008, the Fermi Gamma-ray Space Telescope has revolutionized our understanding of the cosmos. Fermi has mapped the entire sky in gamma rays, the highest-energy form of light, and detected thousands of sources so far. In celebration of its 10th anniversary in space, here are five of its transformative discoveries. In 2017, Fermi saw a gamma-ray burst coming from the constellation Hydra. The burst was tied to ripples in space-time detected by the Laser Interferometer Gravitational Wave Observatory, operated by the National Science Foundation. This was the first time light and gravitational waves were detected from the same source. Scientists believe the event formed when two neutron stars merged. The merger created the gravitational signal and a jet of particles traveling at nearly the speed of light that gave off gamma rays. In 2009, Fermi used a short-duration gamma-ray burst to confirm that all light travels at the same speed, no matter its energy. This proved Einstein's theory that space-time is smooth and continuous. Early in Fermi's mission, scientists noted odd structures emerging from above and below the Milky Way. These bubbles, spanning 50,000 light-years, were produced by our galaxy's supermassive black hole and are only a few million years old. In 2013, Fermi studied the remains of two supernovas to learn more about cosmic rays, particles traveling at nearly the speed of light. It was hard to find the source of cosmic rays because they veer off course as they travel and encounter magnetic fields. Fermi showed that gamma rays from these supernova remnants came from cosmic rays that were accelerated by the explosions' blast waves. Fermi has seen 5,000 terrestrial gamma-ray flashes in the last 10 years. These flashes are associated with lightning and thunderstorms in Earth's atmosphere. From Earth, to the farthest reaches of the cosmos, Fermi's first ten years have fundamentally altered how we look at the universe. Who knows what mysteries remain to be solved? [Beeping] [Beeping]