In his theory of general relativity Einstein predicted that the gravity of large objects should alter the path of light travelling towards us.
This results in a phenomenon known as ‘gravitational lensing’ in which the faint light from distant galaxies is ‘bent’ around intervening massive galaxies, creating a ring or arc of luminous features around the closer object.
Such ‘gravitational lenses’ are very rare – with only around 500 discovered so far – but have many applications that are important for astronomers and cosmologists, including providing a window on the distant, and so early, Universe and allowing elusive dark matter in massive lensing galaxies to be weighed.
The Zooniverse citizen science project Space Warps recently reported that its online volunteers have helped to discover 29 new gravitational lenses, and 30 other possible lenses from the Canada France Hawaii Telescope Legacy Survey.
Not only are these important discoveries in their own right but they also prove just how good citizen scientists are at hunting down unusual objects.
The results from Space Warps, which is jointly led by researchers at Oxford, SLAC in the US and Kavli IPMU in Japan, are to be published in two papers in MNRAS.
‘This survey has already been searched by automated lens-finding algorithms (or "robots"), and these potential lenses weren't captured, so it just goes to show what an army of sharp-eyed human volunteers can do!’ Aprajita Verma of Oxford University’s Department of Physics, one of the leaders of the Space Warps project, told me.
But, as Aprajita explains, Space Warps has built on the approach pioneered by the Zooniverse and its family of research projects to get volunteers even more involved.
‘Citizen scientists helped us design the project and after potential lenses were identified a number of them (including moderators Elisabeth Baeten, Julianne Wilcox, Christine Macmillan and Claude Cornen) modelled these candidates to see if they were plausible.’
‘It felt great to part of the team and to be involved in so many ways. I felt even more responsible for the project and even protective of it,’ reveals Elisabeth Baeten. ‘And as a moderator you are responsible for the new citizen scientists. You want to help and guide them on the one hand and on the other hand you don't want to dampen their enthusiasm because for them everything is new and strange.’
‘Space Warps is the first Zooniverse project where citizen scientists were involved from the very beginning and were included in the science team right up to being co-authors on the papers. It doesn't get much better than that!’, Elisabeth added.
All development for the project, including writing the scientific papers, took place on the public GitHub platform, allowing the volunteers to be involved at every stage.
‘Citizen scientists and web developers are co-authors on the papers alongside the project scientists, it’s this combined effort that’s made our study possible,’ Phil Marshall, Space Warps co-lead from SLAC (US) comments.
In the research papers the authors detail a new way of interpreting the classifications of the citizen scientists and, with the help of the Oxford e-Research Centre, a similar technique will be adopted by future Zooniverse projects.
But what about the future of cosmic lens hunting?
‘Space Warps can continue to provide a means for efficient lens finding,’ Anupreeta More, Space Warps co-lead from IPMU Japan, tells me. ‘As we enter an era of wide and sensitive imaging surveys that will contain thousands of lenses we need to look at millions of galaxy images to find them and that’s something we’ve proved citizen scientists are absolutely brilliant at!’