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[Music throughout] Announcer: Liftoff of the Delta rocket carrying a gamma-ray

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telescope searching for unseen...[Fades out] Narrator: I'm Julie Mcenery, Fermi

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Project Scientist. Since its launch in 2008,

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the Fermi Gamma-ray Space Telescope has revolutionized our understanding of

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powerful events and objects in the cosmos. Fermi observes the universe using

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gamma rays, the highest-energy form of light, more energetic than even X-rays.

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Gamma rays are emitted by objects with extreme gravity and magnetic fields.

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Many of the gamma rays Fermi sees are produced by black holes,

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and incredibly dense, rapidly spinning stars called pulsars.

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Fermi's predecessor, the Compton Gamma Ray Observatory, collected data

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from 1991 to 2000, which was used to create this all-sky map.

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Over the past decade, Fermi has

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refined our view and fundamentally changed our understanding of the cosmos.

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In celebration of its 10th anniversary, here are just a few

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of its transformative discoveries. In its very first

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year of observations, Fermi spotted a short, powerful gamma-ray burst

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called GRB 090510. This burst

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provided proof that space-time works the way Einstein predicted.

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Gamma-ray bursts are the most luminous events Fermi sees.

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Scientists think they are caused when stars collapse, or when neutron stars or black holes

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merge. These events drive jets of particles at nearly the speed of light.

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The material in the jets collides, generating shock waves that produce the

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gamma rays that we see. In the last decade, Fermi has detected over

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2.300 bursts. Fermi detected two gamma rays

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with different energies from GRB 090510. Although

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they traveled over 7 billion light-years, both reached Fermi at nearly the same

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instant. This supports Einstein's theory that all light

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no matter its energy, moves at the same speed because space-time is smooth.

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In 2017, Fermi spotted a gamma-ray burst

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coming from the constellation Hydra, which coincided with the detection

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of ripples in space-time. The burst came from the merger of

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two superdense neutron stars. Ground-based observatories

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detected gravitational waves at nearly the same instant Fermi detected gamma rays.

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This was the first time light and gravitational waves were detected

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from the same source. Early in Fermi's mission,

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scientists noticed odd structures emerging from above and below the

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Milky Way. These Fermi "bubbles" have become more prominent with each passing year

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of data. The bubbles extend 25,000 light-years

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above and below the galactic plane. They were probably produced only

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a few million years ago by the supermassive black hole at the center of the Milky Way.

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This means our galaxy was extremely active a very

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short time ago, in astronomical terms.

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Over the last 10 years, Fermi has also placed new limits on

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theories about dark matter by looking at tiny, faint galaxies called dwarf spheroidals.

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Almost 85 percent of the universe's matter is dark matter,

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but scientists don't know exactly what dark matter is.

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One theory is that it's made of Weakly Interacting Massive Particles,

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or WIMPs. WIMPs don't produce light, or interact with

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other particles. When two WIMPs meet, though, scientists think

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they annihilate and produce gamma rays with unique signatures.

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Dwarf spheroidals have high concentrations of dark matter.

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Fermi has observed several of these galaxies, but seen no sign of

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WIMP-produced gamma rays. This sets strong limits on the properties

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of dark matter. The universe is a sea of

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charged particles called cosmic rays, moving at nearly the speed of light.

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Fermi observations of two supernova remnants shed new light on their origins.

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Thousands of cosmic rays hit every square meter of Earth's atmosphere

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every second. And Fermi's Large Area Telescope

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detects only one gamma ray for every thousand cosmic rays. Despite their

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abundance, the origins of cosmic rays were a longstanding mystery.

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In 1949, Enrico Fermi, the satellite's

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namesake, proposed that they might be generated in the shock waves of supernovas.

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But cosmic ray paths are hard to trace. They veer off course each time

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they encounter a magnetic field. In 2013,

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Fermi observed gamma rays coming from two supernova remnants.

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The gamma rays' properties told scientists they were created by cosmic rays propelled by

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supernova shock waves, just as Enrico Fermi predicted.

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While the atmosphere is pelted by cosmic rays from above, thunderstorms

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generate gamma rays from below. Fermi observes these

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terrestrial gamma-ray flashes, or TGFs, using its Gamma-ray Burst Monitor.

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Under the right conditions, a lightning flash triggers a flood

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of electrons that rush to the top of the cloud at nearly the speed of light.

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These electrons produce gamma rays when they run into air molecules.

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Fermi has spotted 5,000 TGFs over

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10 years. but scientists estimate more than a thousand of them occur every day.

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From Earth's atmosphere, to the farthest reaches

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of the cosmos, Fermi's first ten years have fundamentally altered how

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we look at the universe. The gamma-ray sky changes every day,

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who knows what new, exciting await us

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in the future?

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[Music]

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[Beeping]

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[Beeping]