Advanced artificial intelligence has identified thousands of possible “gravitational lenses” – distortions in spacetime predicted by Albert Einstein – that promise to improve our understanding of dark matter and galaxy evolution.
Einstein realized that mass distorts space, and massive galaxies and galaxy cluster can distort the space around them so much that they form a cosmic lens, bending and magnifying the path of light from more distant galaxies through this distorted space.
Gravitational lenses are important tools for cosmologists. They can magnify the light of distant galaxies that are too faint to otherwise see in detail, or make visible where they cannot be seen Dark matter distorts space. However, only about a hundred good gravitational lenses were available to astronomers.
Related: Lens of Nature: How gravity can bend light like a telescope
Now a team led by Kim-Vy Tran, an astronomer at ASTRO 3D (the ARC Center of Excellence for All Sky Astrophysics in 3 Dimensions) and the University of New South Wales in Australia, has used a machine learning algorithm called the Convolutional Neural Network to Search for gravitational lenses in images taken by the Dark Energy Camera (DECam) of the Victor M. Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory in Chile.
Developed by Colin Jacobs of Swinburne University of Technology in Australia, the algorithm sifted through tens of millions of images of galaxies to select a sample of 5,000 possible gravitational lenses not immediately apparent to the human eye.
“These lenses are very small, so if you have blurry images, you won’t really be able to see them,” Tran said in a expression (opens in new tab).
Tran and her team used the telescopes in the WM Keck Observatory in Hawaii and the Very large telescope in Chile to follow up on 77 of the 5,000 candidate lenses. They found 68 of these lenses to be real and confirmed this spectroscopically redshifts of both the lens and the object being lensed for 53 of them. The lenses typically have a higher redshift than most previously known lenses, meaning astronomers can use them to see deeper into the Universe.
The algorithm’s 88 percent success rate in finding new lenses means astronomers now have potentially thousands of new lenses to choose from, although Tran said the team’s goal was more modest.
“Our goal…is to spectroscopically confirm around 100 strong gravitational lenses that can be observed year-round from both the northern and southern hemispheres,” she said.
The lenses’ average redshift is 0.58, which corresponds to a distance of about 5 billion light-years, while the distant objects magnified by the lenses typically have a redshift of about 1.92, meaning their light is about 10 Billions of years ago.
“With these lenses at different distances, we can look at different points on the cosmic timeline to follow how things are changing over time, from the very first galaxies to today,” Tran said.
“Usually these galaxies look like small, fuzzy blobs, but the lens magnification allows us to see their structure with much better resolution,” says Tucker Jones, associate professor in the Department of Physics and Astronomy at the University of California, Davis, and a member of the research team said in the statement.
The lenses therefore offer promising targets for follow-up with observatories like the one Hubble Space Telescope and the James Webb Space Telescope.
The study was published on September 26th The Astronomical Journal.
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