Plate Nº 85 · recorded October 22, 2026
Space & AstronomyReported finding
Hubble Images Gravitational Lens to Prepare for Roman Telescope
NASA's Hubble has imaged a gravitational lens magnifying a galaxy eight billion light-years away — early groundwork for the Nancy Grace Roman Space Telescope.
By Marcus Bennett3 min read638 words
In brief
- The lens's foreground elliptical galaxy lies about 4.5 billion light-years away; the magnified background galaxy lies about eight billion light-years away.
- The lens shows an arc-counterarc pair: the same background galaxy appears as a large arc and a smaller, flipped arc on opposite sides of the foreground galaxy.
- Dark matter makes up the majority of the universe's mass; lensing distortions let researchers measure it in foreground galaxies.
- Hubble views mainly visible and ultraviolet light at high resolution; Roman sees mainly infrared with a much wider field of view.
- Astronomers are building a computer model from Hubble lens images to analyze dark matter distortions in Roman's future large surveys.
A galaxy sitting 4.5 billion light-years from Earth is bending and magnifying the light of another galaxy nearly twice as far away, and NASA's Hubble Space Telescope has just released the image of that alignment. The observation is not a one-off: it belongs to a systematic campaign of gravitational lensing images Hubble is collecting to prepare for science with the incoming Nancy Grace Roman Space Telescope.
The image itself rewards a closer look. A sweeping barred spiral galaxy — so called because its arms extend from a central bar of stars — dominates the frame. Astronomers think our own Milky Way, roughly the same size, is a barred spiral too. But the scientific prize sits in the lower-right corner: a gravitational lens.
What is a gravitational lens?
Gravitational lensing occurs when the mass of a foreground object, such as a galaxy, warps spacetime itself. Light from a background source bends, distorts and magnifies as it passes around that object — the foreground galaxy acts like a giant lens in space. These alignments require a precise, chance coincidence between the foreground and background galaxies.
In the new Hubble image, the lens consists of a reddish elliptical foreground galaxy about 4.5 billion light-years away. The light we receive from it now started traveling toward us when our solar system was still forming. The background galaxy lies about eight billion light-years away — almost twice the distance.
It appears twice. A large, very noticeable arc sits to the upper left of the foreground galaxy; a much smaller, flipped image of the same background galaxy sits to the lower right. Astronomers call this configuration an arc-counterarc pair.
How does a lens weigh dark matter?
The mechanism matters for practitioners. The more massive the foreground galaxy, the stronger the lens and the more it bends light. By measuring how the background galaxy is distorted, researchers can calculate how much mass the foreground galaxy contains.
That calculation feeds directly into dark matter research. Dark matter is the mysterious, invisible substance that makes up the majority of the universe's mass. The visible matter alone cannot account for the observed level of distortion in the background galaxy. The mismatch lets researchers pin down both the total mass of the foreground galaxy and its dark matter content.
Almost every object in the frame is a galaxy, apart from a few scattered foreground stars. A tiny spiral to the left of the large barred spiral may be a satellite galaxy, similar to the Large and Small Magellanic Clouds that orbit the Milky Way.
Why do Hubble and Roman need each other?
The two telescopes cover different territory. Hubble views the cosmos primarily in visible and ultraviolet light, with some infrared coverage, and delivers high-resolution views of individual objects. Roman sees mainly infrared wavelengths plus some visible light, and carries a much larger field of view suited to wide panoramas.
That division of labor shapes the lensing strategy. Hubble can observe these gravitational lenses only one at a time. Roman's wide view of the sky will deliver a far larger sample of lenses once it begins operating.
Astronomers are using Hubble's sharp images now to build a computer model that better analyzes dark matter-induced distortions. That tool will help them process Roman's large images later. Hubble will also follow up on interesting lenses that Roman detects, closing the loop between the two observatories.
The credits for the image list NASA, ESA, and X. Huang of the University of San Francisco, with image processing by Gladys Kober of NASA and the Catholic University of America.
Together, the two telescopes aim to build a more comprehensive picture of the cosmos — one lens at a time.
Media contact for the release: Claire Andreoli, NASA's Goddard Space Flight Center, Greenbelt, Maryland.
via nasa.gov (Original)
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News editor covering regulation, policy and their impact on general science news at SciBeat.
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