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[Music]

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Narrator: Dark matter makes up about 27 percent

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of the cosmos, but so far no one knows what it is.

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Dark matter neither emits nor absorbs light and it

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interacts with the rest of the universe primarily through gravity.

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In fact, it's thought dark matter traced the initial framework of the

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cosmos, attracting normal matter that formed stars and galaxies.

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Black holes are astronomical objects famed for their

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extreme gravity. Jeremy Schnittman, an astrophysicist at

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NASA's Goddard Space Flight Center, wondered if they could serve as a kind of

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laboratory for exploring different dark matter models. [Dr. Schnittman]: The leading

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particle physics model for dark matter is called weakly

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interacting massive particles, or also known as WIMPS. These guys just

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fly through the universe without even bumping into anything

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or each other. The idea of two WIMPS coming together,

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annihilating, and forming gamma rays, is kind of like two bullets hitting

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head-on in a crossfire--it's very rare. But when you

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go to the area around a supermassive black hole, we expect the

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density to be much higher so the probability of annihilation is much higher

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and thus detection with a gamma-ray telescope.

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Narrator: In Schnittman's computer simulation, a population

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of dark matter particles orbits a rapidly spinning black hole.

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Close in, at the brink of the black hole's event horizon, the particles

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are orbiting at nearly the speed of light. The lightly shaded region

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farther out is the ergosphere, a zone where all particles are forced

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to move in the same direction as the black hole's spin.

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The concentrated dark matter collides and makes gamma rays,

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but not all of this light can escape the ergosphere. The gamma rays

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most likely to make it out come from the left side, where the black hole spins

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toward us. The result is an asymmetric glow.

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The highest energy gamma rays come from the center of this region,

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corresponding to the black hole's equator. Schnittman's work has

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uncovered previously overlooked orbits that can produced extremely energetic

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gamma rays, and has shown that the peak energy attainable for this escaping light

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is a strong function of the black hole's rotation.

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So far, the initial work is focusing on setting upper limits on dark matter

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annihilation rates by looking at otherwise quiescent galaxies. But Schnittman's

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ultimate ambition is nothing short of an unambiguous detection of dark matter

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annihilation around supermassive black holes. [Dr. Schnittman]: To me,

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dark matter, black holes, two of the most elusive things in the

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universe coming together to help explain each other

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is quite poetic. [Music]