Hubble gallery of galaxy 'lenses' found by a USF team sets up NASA's new Roman telescope to test a theory of dark matter

Nine new Hubble Space Telescope images show faraway galaxies bent into rings and arcs by the gravity of nearer galaxies, and astronomers plan to use them with NASA's new Roman Space Telescope to test the leading theory of dark matter, NASA's Nov. 12 release says.  The images are credited to Xiaosheng Huang of the University of San Francisco, whose team of mostly undergraduates finds such lenses with AI.

Why it matters

Dark matter is unseen material that gives off no light; astronomers detect it only by its gravity.  The leading theory, called cold dark matter, predicts that galaxies are wrapped in many small dark clumps weighing 1 million to 1 billion times the Sun.  For scale, the dark matter around our Milky Way weighs about 1.3 trillion Suns, so even the biggest predicted clump is about 1/1,300 of that.  A clump in front of a stretched arc should leave a small kink in it.  Finding those kinks, or failing to, would support or undercut the theory.

How a lens works

Einstein's theory of gravity says a heavy object bends passing light.  When a distant galaxy sits almost exactly behind a closer one, the closer galaxy acts like a magnifying glass and smears the far one into arcs.  How much the arcs are warped tells astronomers how much the closer galaxy weighs, dark matter included.

The release points out several shapes in the gallery:  an Einstein ring, where the line-up is so exact that the far galaxy wraps nearly all the way around; galaxies copied four times; a matched pair of arcs on opposite sides; and a rare lensing galaxy with a dark dust lane slicing across a possible ring.  Blue arcs are galaxies full of young stars; red arcs hold older stars.

The release gives no distances.  Huang's team has reported that its lensing galaxies sit at redshifts of 0.1 to 1, a measure of distance, which means their light left them about 1.4 billion to 7.9 billion years ago.  The magnified galaxies behind them are farther still.

Where the lenses came from

Huang's group trained neural networks, a type of AI, on survey images taken for DESI, the Dark Energy Spectroscopic Instrument on the 4-meter Mayall telescope at Kitt Peak National Observatory in Arizona.  The search turned up about 3,500 candidates, the team reported in a peer-reviewed paper in The Astrophysical Journal, and Hubble confirmed 50 of the 51 it checked; one is still unclear.  The lenses in the new gallery were first spotted in DESI data, the release says.  Huang's team also works with DESI scientists at Lawrence Berkeley National Laboratory.

The two telescopes

Hubble, launched in 1990, has a 7.9-foot (2.4-meter) main mirror and sees mostly visible and ultraviolet light, so it gives the sharpest view of a single object.  Roman has a mirror the same size but sees mostly infrared light, across a view at least 100 times wider than Hubble's, so each picture should catch many more lenses.  Roman launched Aug. 30 on a SpaceX Falcon Heavy from Kennedy Space Center in Florida and works about 1 million miles from Earth, roughly four times the Moon's distance.  Its main mission lasts five years, and its lifetime cost is $4.3 billion.

The plan is to train software on Hubble's sharp lens images so it can find similar arcs in Roman's wide ones, then point Hubble back at the most interesting finds for close-ups.

What's proven

The lenses themselves are confirmed by Hubble's pictures.  The dark matter test has not been run; the release describes plans, not results.  These lenses can't be seen in a backyard telescope:  they are faint galaxies billions of light-years away.

Source:  NASA Science, "NASA's Hubble Offers Cosmic Sampler of Targets for Roman" (Nov. 12, 2026); Huang et al., "DESI Strong Lens Foundry I:  HST Observations and Modeling with GIGA-Lens", The Astrophysical Journal; University of San Francisco, Xiaosheng Huang faculty page; Lawrence Berkeley National Laboratory, Huang seminar abstract (May 6, 2021); DESI; NASA Science, Roman FAQ, technical details and launch page; NASA, Roman replan note (Oct. 14, 2021); NASA Science, Hubble mission page.  Look-back times, the clump-to-Milky Way ratio and the Moon comparison are the Daily News's own arithmetic.  Drafted by AI for San Jose using NASA source material.  NASA did not write or review this story.