How to find invisible black holes

I wrote an article about our recently-launched Black Hole Hunters project for the Open University’s OpenLearn web site:

Finding the sudden glints of light from otherwise invisible black holes is the focus of the SuperWASP: Black Hole Hunters citizen science project. In citizen science projects, we ask volunteers – you! – for help figuring out things that computers can’t solve for us! Black Hole Hunters is the Open University’s second citizen science project using data from the SuperWASP All-Sky Survey.

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Whereas SuperWASP Variable Stars looks for types of star that repeatedly change in brightness at regular intervals, SuperWASP: Black Hole Hunters is searching for the invisible black holes. The two projects are very similar, except now we’re looking for stars that get brighter only once before going back to ‘normal’. The lensing effect – where the black hole’s gravity bends and focuses the light from its companion star – makes a short, symmetrical peak in the graph of the star’s brightness.