Members of the public are invited to identify rare gravitational lenses
University of Portsmouth experts have developed the machine learning algorithm being used to select strong gravitational lenses in sky images from the Euclid space telescope as part of new project Space Warps.
Space Warps invites people to identify rare gravitational lenses, which can be used to magnify distant galaxies that conventional telescopes can’t detect.
When one of these gravitational lenses happens to sit right in front of a background galaxy, the magnification factor can be up to x10 or even more, giving a zoomed-in view of the distant universe, just at that particular point.
Lenses can help investigate young galaxies more than halfway across the universe, as they formed stars and started to take on the familiar shapes we see nearby.
This is already the largest dataset of strong lenses ever observed from space, but it is just the tip of the iceberg. Euclid will cover 300 times more sky over the next five years and that will allow us to produce a revolutionary sample of over 100,000 strong lenses. The ongoing contributions of citizen scientists will be critical to enabling those discoveries.
PhD student Natalie Lines, from the University’s Institute of Cosmology and Gravitation, said: “Currently the best tool for detecting gravitational lenses is the human brain, but we cannot get humans to inspect over one million objects, so colleagues and I have developed machine learning models able to pick out ‘candidates’ that are most likely to be lenses to pass on to citizens to visually inspect.”
Human beings have a remarkable ability to recognise patterns and detect the unusual with only minimal training. With a basic understanding of what the distorted images of galaxies that have passed through a gravitational lens look like, participants in the Space Warps project can help discover new examples of this amazing phenomenon, and enable survey scientists to carry out new investigations of stars and dark matter in the universe.
Without being taught what to look for by humans, AI algorithms struggle to detect lenses, but together, humans and AI can accurately spot thousands of lenses.
Natalie added: “We have imaging from the Euclid telescope that covers around 50 square degrees, from which we want to find all the strong gravitational lenses. However, strong lensing is very rare, and of the around one million objects that we have in this 50 square degrees, we’re expecting to find a few hundred lenses.
“This is particularly exciting as this is likely to be one of the largest single datasets of strong lenses we have to date - and it’s only going to grow as Euclid collects more data.”
The European Space Agency’s (ESA) Euclid space telescope launched in July 2023 and has begun surveying the sky. Splitting the sky up into chunks, Euclid aims to take an image of each chunk and mosaic them together to produce the most detailed map of the Universe ever obtained.
Artist's impression of the Euclid spacecraft. Copyright: ESA/C. Carreau
Euclid has been designed to look at a much larger region of the sky than the Hubble Space Telescope or the James Webb Space Telescope, meaning it can capture a wide range of different objects all in the same image – from faint to bright, from distant to nearby, from the most massive of galaxy clusters to the smallest nearby stars.
With Euclid, there is both a very detailed and very wide view of the sky all at once. The analysis of this rich data set is coordinated by the international Euclid Consortium, whose 2600+ members from 18 countries are working on various problems regarding astrophysics and cosmology. Above all, their goal is to constrain the nature of dark matter and dark energy, and to answer fundamental questions on how galaxies form and evolve.
Professor of Astrophysics, Thomas Collett, who leads the gravitational lensing group at the University, said: “This is already the largest dataset of strong lenses ever observed from space, but it is just the tip of the iceberg. Euclid will cover 300 times more sky over the next five years and that will allow us to produce a revolutionary sample of over 100,000 strong lenses. The ongoing contributions of citizen scientists will be critical to enabling those discoveries. Once we’ve found all those lens systems, we will use them to probe the way galaxies form, the laws of gravity and the constituents of the Universe - key objectives of the Euclid mission.
This recent Space Warps project was launched by the Euclid Consortium and the Zooniverse team.
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