The universe is a big place, filled with objects and structures so large that their masses bend the light that passes by, sharpening the photons emanating from more distant light sources. These “gravitational lenses” can reveal very ancient parts of the universe, which otherwise would be too fuzzy or faint for Earth-based observers to spot.
Now, a team of researchers at Lawrence Berkeley National Laboratory has spotted a configuration of galaxies they believe are an especially exquisite gravitational lens. The lens—now dubbed the Carousel Lens—consists of seven background galaxies around a core foreground galaxy cluster, as well as a smattering of other lensed sources on its periphery.
The lens is “a chance alignment of multiple galaxies across a line-of-sight spanning most of the observable universe,” explained David Schlegel, an astrophysicist at Berkeley Lab and co-author of the paper, in a laboratory release. “Finding one such alignment is a needle in the haystack. Finding all of these is like eight needles precisely lined up inside that haystack.”
Gravitational lenses are useful for seeing ancient light sources like the oldest known star or a supernova that reappeared in the sky multiple times as its bent light took different paths to Earth. The unique overlay of the Carousel Lens makes it a particularly strong gravitational lens.
The research team also generated a computational model of the lens and calculated the approximate distances of the galaxies. The lensing cluster is about five billion light-years from Earth, and its seven galaxies are anywhere between 2.6 to 7 billion light-years beyond that—so up to 12 billion light-years into the past, according to the study, published last week in The Astrophysical Journal.
“As they appear through the lens, the multiple images of each of the background galaxies form approximately concentric circular patterns around the foreground lens, as in a carousel,” said Xiaosheng Huang, a physicist and astronomer at the University of San Francisco and co-author of the study, in the same release. “It’s an unprecedented discovery, and the computational model generated shows a highly promising prospect for measuring the properties of the cosmos, including those of dark matter and dark energy.”
Some gravitational lenses form Einstein rings, or near-perfect circles of light in the sky; last year, a team found signatures in Einstein rings that suggested axion-like dark matter may inhabit the background galaxies. In the recent team’s lens, an Einstein Cross indicates the symmetrical distribution of mass (including dark matter) across the lens.
The new lens will allow researchers to study the nature of dark matter and dark energy, which together make up about 95% of the universe, according to NASA. That’s right: all we’ve ever observed only accounts for 5% of everything. But now we have another window into the inner workings of that everything.
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