Dark matter circling the drain of a massive black hole could radiate gamma-rays that might be visible from Earth, according to new research.

Dark matter is five times more plentiful in the universe than regular matter, but it does not emit, reflect or absorb light, making it not just dark but entirely transparent. But if dark-matter particles around black holes can produce gamma-rays (high-energy light), such emissions would give scientists a new way to study this mysterious material.

The process responsible for creating the gamma-rays is somewhat counterintuitive, because it seems to defy two common assumptions: that nothing can escape from a black hole and that there's no such thing as a free lunch. [Images of Dark Matter Throughout the Universe]

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