JWST Spots 104 Magnified Stars in the Dragon Galaxy — A New Record That Could Reveal the Nature of Dark Matter
The James Webb Space Telescope has watched more than 100 individual stars flare into view inside a single faraway galaxy — and the result may help scientists answer one of the biggest open questions in physics: what dark matter actually is.
Astronomers found 104 separate “magnified stellar events” in a galaxy nicknamed the Dragon, about 6.5 billion light-years from Earth. That is more than double the previous record of 44 such sightings in the same galaxy, and the largest collection of highly magnified stars ever found in one galaxy.
The study, led by José María Palencia of the Institute of Physics of Cantabria in Spain, was published in the journal Astronomy & Astrophysics on 30 September 2026. It is the first statistical study of more than 100 magnified stellar events at this distance — and it turns a distant, stretched-out galaxy into a natural laboratory for studying both giant stars and the invisible matter that shapes the universe.
What exactly did astronomers see?
The Dragon is not an ordinary galaxy. It sits behind a huge cluster of galaxies called Abell 370, and the cluster’s gravity bends and stretches the Dragon’s light into a long, thin curve known as the Dragon arc. The effect is called gravitational lensing: a massive object in front acts like a magnifying glass for whatever lies behind it.
But the lensing is not smooth. Along certain lines in the lens, called caustics, the light can be focused so strongly that a single star’s brightness shoots up hundreds or even thousands of times. When a star in the Dragon drifts across one of these lines, it flares up, stays bright for a few days or weeks, and then fades away again. Astronomers call these moments caustic-crossing events.
The team compared images of the Dragon taken by Webb’s NIRCam camera between 2022 and 2024, across three observing cycles and four different filters. By carefully subtracting one image from another, they could spot tiny changes in brightness — the fingerprints of individual stars crossing the caustics.
After removing false alarms, such as bright objects that had nothing to do with the Dragon, and merging repeated sightings of the same event, the researchers were left with 104 unique events. As the paper puts it, this is “the largest sample of highly magnified star candidates identified in a single galaxy”.
Why only giant stars show up
There is a catch to this kind of stargazing: only the brightest stars can be seen at all. Even with Webb’s giant mirror and the extra boost from gravitational lensing, an ordinary star like our Sun would still be far too faint at a distance of 6.5 billion light-years.
The stars that do appear are almost always supergiants — stars many times bigger and thousands of times brighter than the Sun. They come in two main types. Blue supergiants are hot and shine mostly in short, blue wavelengths. Red supergiants are cooler and glow mostly in the near-infrared.
Counting how many of each type appear tells astronomers something about the galaxy itself. A young, metal-poor galaxy — one whose stars contain few elements heavier than hydrogen and helium — tends to produce more bright blue supergiants. An older galaxy, or one richer in heavy elements, leans towards the red.
In the Dragon, the team found roughly equal numbers of blue and red supergiants, a ratio of about one to one. That suggests the Dragon is “a relatively evolved, still star-forming system” — a galaxy that has been around long enough to build up older stars, but is still busy making new ones.
That matters because the light we see from the Dragon left the galaxy when the universe was only about half its current age. In other words, Webb is giving us a census of giant stars in a galaxy as it was billions of years ago — something no telescope could do for an unlensed galaxy at that distance.
The Dragon arc: a famous cosmic magnifying glass
The Dragon arc has a special place in astronomy. It was the first giant arc ever discovered, spotted in the late 1980s, and it remains one of the best-studied examples of gravitational lensing in the sky.
Its power comes from Abell 370, a massive cluster of galaxies sitting between us and the Dragon. The cluster is about 6 billion light-years away in its own right, and its combined gravity — from hundreds of galaxies plus huge amounts of dark matter — warps the space around it. Light from the Dragon, travelling towards Earth, passes through that warped space and is bent, stretched and magnified.
Because the cluster is not a smooth, uniform blob, its gravity bends light by different amounts in different places. The result is the long, curved Dragon arc, crossed by several powerful caustics. That is what makes this one galaxy such a good target: it is stretched across lines where the magnification is strongest, so many individual stars get their moment in the spotlight.
An earlier study of the same galaxy, published in Nature Astronomy in 2025, had already found more than 40 such events from just two sets of Webb images taken a year apart. The new study added a third year of data and a more careful search, pushing the total past 100.
A possible hint about dark matter
The most intriguing part of the new study is not the stars themselves, but what their pattern might say about dark matter.
Dark matter is the invisible material that makes up most of the matter in the universe. We know it is there because of its gravity — galaxies spin too fast and clusters bend too much light for the visible matter alone to explain — but nobody knows what it is made of.
One idea is that dark matter is made of extremely light, wavelike particles. This is called “fuzzy” dark matter. If that is true, the tiny ripples in the lensing pattern should look slightly different from what heavier, particle-like dark matter would produce.
The stars and dark matter inside the Abell 370 cluster can split a caustic line into many smaller “microcaustics”. As the Dragon drifts slowly behind the cluster, its stars cross these microcaustics one by one. So the pattern of where the flares appear — how many show up on each side of the critical curve, the line where magnification is strongest — carries information about what is doing the bending.
The team counted the events on both sides of the critical curve. Far from the curve, the numbers looked the same on both sides. But close to the curve, the count dropped on one side and stayed the same on the other. That pattern fits the fuzzy dark matter model.
It is important to be clear about what this does and does not mean. The researchers themselves say this “could provide a hint of a fuzzy nature of dark matter”, but they add that the same pattern “may also arise from an incorrect location of the critical curve in the lens model”. In plain words: it is a clue, not proof. The lens model — the map of how Abell 370 bends light — still has uncertainties, and a slightly wrong map could produce the same pattern.
That is why the team describes the method, rather than this single result, as the real advance. Apply the same counting technique to other strongly lensed galaxies, take repeated images more often, and build better lens models, and the pattern should become clearer. Over time, this kind of work could become a practical tool for testing what dark matter is made of — not by looking at dark matter directly, which nobody can do, but by watching how it bends the light of distant stars.
Why this matters for astronomy
The Dragon study shows how far Webb has taken a field that barely existed a few years ago. Before Webb, astronomers had spotted only a handful of individual stars at such distances, and each one was a rare, lucky find. Now a single galaxy has yielded more than a hundred.
That changes what is possible. With a sample of 104 events, astronomers can start doing statistics — comparing blue and red supergiants, testing lens models, and looking for patterns that a handful of stars could never reveal. The same approach can be used on other lensed galaxies, building up a picture of what the brightest stars looked like across the universe’s history.
It also shows the value of patience. The team did not need a new telescope or a new instrument. They used images Webb had already taken over three years, compared them carefully, and found something nobody had seen before. As Webb keeps observing the same fields, more events will appear, and the picture will keep getting sharper.
For now, the Dragon holds the record: 104 stars, each one briefly magnified hundreds or thousands of times by a cosmic lens, each one a small flash of light from a galaxy as it was when the universe was half its present age. And hidden in the pattern of those flashes may be a clue to the nature of the invisible matter that holds the universe together.
Frequently Asked Questions
What is the Dragon galaxy?
The Dragon is a distant galaxy about 6.5 billion light-years away, at a redshift of about 0.725. Its light is stretched by the gravity of the galaxy cluster Abell 370 into a long, thin curve called the Dragon arc. It was the first giant gravitational arc ever discovered.
What is a caustic-crossing event?
It is a brief flare-up of a single distant star. The gravity of a galaxy cluster can focus a star’s light so strongly that the star becomes hundreds or thousands of times brighter for a few days or weeks as it drifts across a line called a caustic. Astronomers find these events by comparing images of the same galaxy taken at different times.
How far away is 6.5 billion light-years?
A light-year is the distance light travels in one year. Light from the Dragon has been travelling towards us for about 6.5 billion years, so we see the galaxy as it was when the universe was roughly half its current age.
What is fuzzy dark matter?
It is one proposed form of dark matter, made of extremely light particles that behave more like waves than like tiny billiard balls. The pattern of magnified stars in the Dragon fits this model, but the result is a hint, not proof — the researchers note it could also come from small errors in the map of how Abell 370 bends light.
Why can Webb only see supergiant stars at this distance?
Even with Webb’s sensitivity and the extra magnification from gravitational lensing, ordinary stars are simply too faint at 6.5 billion light-years. Only supergiants — stars many times larger and thousands of times brighter than the Sun — shine brightly enough to be detected.
What happens next?
Astronomers plan to apply the same method to other strongly lensed galaxies, observe them more often, and build better models of the lensing clusters. More events and better models should show whether the fuzzy dark matter hint holds up, and build a bigger census of giant stars in the distant universe.
Sources
- Phys.org, “JWST tracks more than 100 magnified stellar events in the Dragon galaxy”, 8 November 2026: https://phys.org/news/2026-11-jwst-tracks-magnified-stellar-events.html
- arXiv, “The first statistical study of over 100 magnified stellar events at a redshift z ≈ 0.725 with JWST”: https://arxiv.org/html/2604.22702
- Astronomy & Astrophysics, DOI: 10.1051/0004-6361/202660640: https://doi.org/10.1051/0004-6361/202660640
This article is for general information and education only. It is not legal or financial advice.
