Astronomers have noticed two huge galaxies locked in a cosmic tug-of-war 700 million light-years from Earth — and for the primary time in such a close-by galaxy, watched as a faint stream of stars is being pulled from one into the opposite.
The observations, made within the galaxy cluster Abell 3667, revealed a faint, million light-year-long bridge of stars connecting its two brightest galaxies. Astronomers say the cluster is definitely the results of two smaller clusters that started merging a couple of billion years in the past, every with its personal dominant central galaxy. As these giants — and their satellite tv for pc galaxies — proceed to merge, the bridge of stars between them presents uncommon insights into the clusters’ historical past and the highly effective gravitational forces at play.
“This is the first time a feature of this scale and size has been found in a local galaxy cluster,” Anthony Englert, a Ph.D. candidate at Brown University in Rhode Island, who led a new paper describing the observations, said in a statement. “It was a huge surprise that we were able to image such a faint feature.”
The bridge is fabricated from intracluster gentle, or ICL, a diffuse glow from stars which were stripped from their dwelling galaxies by intense gravitational forces. Englert and his crew had been in a position to detect this dim bridge by stacking 28 hours of observations taken over a number of years utilizing the Dark Energy Camera on the Cerro Tololo Inter-American Observatory in Chile.
“It was just a happy coincidence that so many people had imaged Abell 3667 over the years, and we were able to stack all of those observations together,” Englert mentioned within the assertion.
At the highest of the bridge lies the lenticular (disc-shaped) galaxy IC 4965, together with a small group of galaxies which might be nonetheless falling into the cluster. At the underside of it’s JO171, a placing “jellyfish galaxy” named for the lengthy tendrils of gasoline trailing from one aspect. As it merges into Abell 3667, JO171 is being stripped of gasoline, shutting down star formation in a part of its ring-like construction, in keeping with the assertion.
Beyond its visible magnificence, the sunshine bridge additionally supplies a worthwhile probe of darkish matter, the invisible substance believed to make up roughly 80% of the universe’s mass. Because intracluster gentle tends to hint the identical paths as darkish matter, it presents an oblique solution to map its distribution, astronomers say.
“The distribution of this light should mirror the distribution of dark matter, so it provides an indirect way to ‘see’ the dark matter,” research co-author Ian Dell’Antonio of Brown University mentioned within the assertion.
The research additionally highlights the form of discoveries which might be anticipated to quickly develop into routine with the upcoming Vera C. Rubin Observatory, scheduled to start full operations later this 12 months or in early 2026. Rubin’s Legacy Survey of Space and Time (LSST) will map the southern sky in unprecedented element over a 10-year interval utilizing the world’s largest digital digicam, bringing to gentle galaxy clusters like Abell 3667.
“What we did is just a small sliver of what Rubin is going to be able to do,” Englert mentioned within the assertion. “It’s really going to blow the study of the ICL wide open.”
This analysis is described in a paper revealed Aug. 5 in The Astrophysical Journal.