Feature Story | 11-Jul-2022

Black hole hunters – A citizen science search for black hole self-lensing

Royal Astronomical Society

A research team from the Open University and the University of Southampton is asking for the public’s help to find some of the most mysterious, elusive objects in the Universe – black holes. By examining data from the SuperWASP survey, the UK's leading extra-solar planet detection programme, the team hope to detect changes in starlight that may provide evidence for the existence of these black holes.

The most massive stars explode when they get old, and what is left of the star after the explosion gets condensed into an extremely small area - a black hole. Containing roughly the same amount of mass as our Sun, and compressed into a space that’s only a few miles across, black holes have a very strong gravitational field that nothing – not even light – can escape. Because of this, black holes can be difficult to detect, but they can often be found when material is falling into them – a process known as feeding. Because of their strong gravitational pull, matter falls in so rapidly that it heats up and emits strong X-rays, allowing feeding black holes to be found.

But not all black holes are feeding. The black holes that the team are trying to detect are hidden because nothing is falling in, so there are no tell-tale x-rays to give them away. Luckily, their gravity can still hint at where they might be. The gravity of a black hole is strong enough that it can bend light from stars, acting like a magnifying glass that makes the star’s light appear brighter for a short period of time.

The team is looking in an archive of over 10 years’ worth of measurements from the SuperWASP survey, trying to find any stars that have been magnified by black holes. But there are a lot of stars to look at, and this isn’t a job that computers can do.

Members of the public can join the search by visiting the Black Hole Hunters project site. All you need to do is look at a few simple graphs of how the brightness of stars changed and let the team know if any look like the types of changes they’re looking for.

Adam McMaster, one of the co-leads of the project, says “I can’t wait to see what we find with the Black Hole Hunters project. The black holes we’re looking for should definitely exist, but none have been found yet. Our search should give us the first hints about how many black holes are quietly orbiting stars, eventually helping us to understand the way such systems form.” He adds, “Finding them is a huge task and it’s not something we could do alone, so it’s great that anyone with access to the Internet will be able to get involved no matter how much they know about astronomy.”


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