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Hi, I'm Elizabeth Hayes, a scientist working on NASA's

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Fermi Gamma-ray Space Telescope. Every 3 hours, the

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Large Area Telescope onboard Fermi builds up a picture of the sky in gamma-rays,

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the most energetic form of light. One thing it sees a lot of is

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blazars, active galaxies whose emissions are powered by supermassive black

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holes. Blazars are extremely active objects.

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Here's one of the most extreme Fermi has seen. It's been known to flare up so brightly

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that, for a few days, it outshines every other gamma-ray source.

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Considering that it's more than 7 billion light-years away, this is an immense

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energy output. At the core of an active galaxy is a supermassive

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black hole that powers jets of particles moving near the speed of light.

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We call it a blazar when one of the jets is pointed in our direction.

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This offers us the best view for seeing dramatic flares when there are changes along

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the jet. Fermi has found about a thousand gamma-ray blazars so far.

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Every day, the gamma-ray sky changes depending on which galaxies are

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in outburst and which are in a quiet phase. Because we're watching them all the time,

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we can track their activity and alert other telescopes to new flare-ups.

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As Fermi continues to watch the sky, it builds a more complete picture of the

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daily lives of these powerful objects. Some of the flares we

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see announce the presence of blazars we've never seen before. And sometimes

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we find a gamma-ray flare that is not from a blazar, which is very exciting.

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We hope to discover new types of gamma-ray-emitting objects that we don't yet know

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about. Right now, nearly one third of Fermi sources cannot be connected

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to any known type of gamma-ray source. Out there in the dark,

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what new discoveries await us?