Why not spend Halloween looking for something truly ghostly and mysterious? Astronomers have created a new competition that asks the general public to generate algorithms that can help spot dark matter in Hubble images.

The contest, called Observing Dark Worlds, aims to capitalize on the ever-growing field of citizen science, where non-experts are asked to sift through data to help make discoveries. While most citizen science projects rely on people’s free time, this contest is looking to give out cash prizes, to the tune of $20,000.

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