Ashlin O’Sullivan talks Motley readers through the crowd labour used in to find new discoveries in our galaxy.


In 1930, Clyde Tombaugh discovered Pluto after spending more than 7000 hours staring into a blink comparator, a device used by astronomers to compare images of the same part of the night sky over time by ‘blinking’ between them. Fast moving objects like an asteroid – or in this case Pluto, which at the time was classified as a planet – stand out as they seem to jump between the two images. 92 years later the methodology for discovering celestial objects in space remains much the same. Thousands and thousands of man hours are still spent looking for anomalies in images space. What has changed is the technology involved and the delegation of the work. While expert researchers still dedicate their careers to searching through millions of images, crowdsourcing and the internet mean that it is no longer solely up to junior astronomers like Clyde Tombaugh to search for new celestial objects in orbit. It can be done by the crowd. 


Backyard Worlds: Planet 9 is a NASA-funded ‘citizen science’ project that uses crowd labour to search through data from the space agency’s Wide-Field Infrared Survey Explorer (WISE) mission. The project hopes to find evidence of the hypothesised ninth planet some experts believe exist in our solar system. Backyard Worlds: Planet 9 presents volunteers with short clips in a flipbook from the WISE database across a time period of about five years. The time between images of the same part of space means that, like in the blink comparator, fast moving objects such as a brown dwarf or a ninth planet will stand out.


So almost a century on, why do we still rely on human eyes to do this work? Why not just feed all the data through some supercomputer and be done with it?


It turns out that images from so far away in space have a lot of noise. Artifacts such as optical ghosts (light that has been scattered through the images) and images of variable stars abound in the data. As these artifacts bounce around the photographs and even change colour, they can easily confuse AI and photo processing software. Technology has not yet progressed beyond the pattern recognition capabilities of the human eye. And so, citizen scientists sign up to the programme and examine the data themselves, flagging anything of interest to bring it to the attention of the professionals, or moving on to the next flipbook if there is nothing but noise and still stars. Objects of note are classified as either a dipole or a mover depending on how fast they flit across the pages of the flipbook. This is a textbook use of micro-task crowd labour, where an organisation has engaged people external to it to work with or for the organisation in solving problems of interest. NASA has outsourced this distinct, repetitive task that requires no more expertise than a pair of eyes to the crowd. 


The advantage to NASA of outsourcing this sort of time-consuming labour to the crowd is obvious – it is extremely cost-effective. The volunteer, citizen science nature of the project means that NASA have access to an international, enthusiastic pool of workers, but do not have to pay people for their time and labour. Existing employees can work on more productive tasks rather than spend their 40 hours a week looking through what most of the time is images of nothing but noise. 


However, there are advantages to those undertaking the crowd labour too. Hobbyists, amateur astronomers, and anyone with an interest in that which exists beyond our own blue earth can spend as little or as much time as they wish making a real contribution to scientific work. Chances of stumbling across Planet 9 may be low, and the work may be tedious, but this has been the nature of planet spotting since we moved beyond those that are visible to the naked eye. Projects like this allow anyone, no matter location or background, to take part in meaningful scientific work. For most people, programmes like Backyard Worlds are as close as they will ever get to the stars. 


In 2021 alone, findings from the project were included in two peer-reviewed papers. One article featured the most detailed map of brown dwarfs (failed stars too small to fuse hydrogen in their cores) to date; and the other details three rare brown dwarfs called extreme T-subdwarfs. These celestial objects are extremely cold, old, and uncommon. Astronomers previously only knew of two other extreme T-subdwarfs – also discovered by Backyard Worlds volunteers. The project is still active five years since its launch in 2017, with 75170 registered volunteers and 374124 total classifications according to its website. Thousands of classifications have been made in the last week alone. While there is still no sight of Planet 9, the project has seen huge success in discovering other celestial objects. Backyard Worlds: Planet 9 is an amazing example of the potential of crowdsourcing. People want to be involved with scientific discovery, and this kind of image analysing is work that needs to be done. It makes perfect sense for NASA to continue to fund such projects as long as the human eye remains the ideal tool for this kind of work. Not only is it an easy source of labour, it also works as a branding exercise for NASA. 


While other scientific organisations may not have the same branding heft as NASA, one can imagine that citizen projects in other disciplines would also see success. There has been a huge uptake in volunteer hours across all the citizen scientist projects hosted on Zooniverse – the platform that provides Backyard Worlds: Planet 9 – since COVID-19 lockdowns. One August week in 2021 saw 100,000 people make millions of contributions, the equivalent of decades of full-time research. Should more scientific organisations embrace the power of the crowd, who knows what kind of discoveries await.

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