Hubble’s new image of a gravitational lens paves the way for the Roman Space Telescope

A galaxy acting as a giant magnifying glass for the light of a far more distant galaxy is the star of the new Hubble Space Telescope image that NASA presented on Thursday, October 22. The shot belongs to a series of observations with which Hubble is preparing the ground for the new Nancy Grace Roman Space Telescope, which is already travelling to its final position.

Roman launched on Sunday, August 30, 2026 at 7:26 a.m. US Eastern time (14:26 Greek time) on a SpaceX Falcon Heavy from Kennedy Space Center in Florida. The new telescope is making a three-month journey to the second Sun-Earth Lagrange point (L2), about a million miles, or 1.6 million km, from Earth.

The two telescopes have a 2.4-metre mirror and the same sharpness, but differ in the breadth of their view. Each Roman image covers a patch of sky at least 100 times larger, and the telescope is designed to survey the sky a thousand times faster. Hubble sees mainly visible and ultraviolet light, Roman mainly infrared. In practice the first gives detailed images of individual objects and the second panoramas.

What the image shows

At the centre is a barred spiral galaxy, with spiral arms that start from a bar of stars in its core, roughly the size of our own Milky Way. To its left a small spiral can be seen, perhaps a satellite galaxy, like the Magellanic Clouds around the Milky Way. Almost everything in the image is a galaxy, apart from a few foreground stars.

The real sight, though, is at lower right: an elliptical galaxy acting as a lens. It lies about 4.5 billion light-years away, so the light we see from it today began its journey to us while our solar system was still forming. Behind it sits the background galaxy, at almost twice the distance, around eight billion light-years. Its light bends around the elliptical and makes it appear twice: as a large, conspicuous arc at upper left and as a much smaller, inverted arc at lower right, on the opposite side. The arrangement is called an arc and counter-arc pair.

How does this happen? Any object with large mass, such as a whole galaxy, warps spacetime around it, and light passing through bends. The result resembles a glass lens: the image of whatever lies behind the galaxy is magnified and distorted. It takes a precise coincidence: the lensing galaxy and a more distant galaxy must line up, from our position, almost in a straight line.

Scientists’ interest is focused on dark matter, the invisible and mysterious substance that makes up most of the universe’s mass. The greater the lensing galaxy’s mass, the more strongly it bends light. Visible matter is not enough to explain the distortion of the background galaxy, so researchers can “weigh” the lensing galaxy, calculating both its total mass and how much dark matter it contains.

Hubble studies one lens at a time, while Roman, with its wide field of view, will collect a much larger sample. Astronomers are already developing, based on Hubble’s sharp images, a computer model that will analyse the dark-matter distortions in Roman’s large images. Hubble will also carry out complementary follow-up observations of the interesting lenses Roman finds.

What comes next: Roman’s first images are expected by early 2027, after the three-month commissioning and testing period. Its main instrument is a 300-megapixel infrared camera with 18 4K detectors. It will send 1.4 terabytes of data a day, the highest data rate of any NASA astrophysics mission so far, and machine-learning tools and citizen scientists will help sort the findings. “Never before could we see the universe with eyes like Roman’s,” said Julie McEnery, senior project scientist at NASA’s Goddard Space Flight Center.