Hubble’s high-resolution imagery allowed researchers to hone in on more of the Bullseye galaxy’s rings — and helped confirm which galaxy dove through its core.
Seabirds like the Northern Gannet dive straight into the ocean to catch fish, sometimes from heights of 100 feet (30 meters). With their sharp, spear-like bills and neatly folded wings, they minimize splash on impact, though the water still ripples outward in small waves.
Now, imagine a similar event unfolding in space — but instead of a bird, picture a tiny galaxy, and instead of the ocean, a much larger galaxy.
About 50 million years ago, a small blue dwarf galaxy plunged through the massive Bullseye galaxy, creating a striking ripple effect. But in space, these “waves” behave differently. Instead of water, the impact pushed gas, dust, and stars both inward and outward, forming at least nine glowing rings in the larger galaxy.
This level of detail is rarely observed in galactic collisions. Data from both the Hubble Space Telescope and the W. M. Keck Observatory in Hawaii confirmed that the Bullseye galaxy has an unprecedented nine rings — six more than any other known galaxy. Hubble also identified the culprit: the blue dwarf galaxy, now positioned just to the left of the Bullseye’s core.
Straight Shot: Hubble Investigates Galaxy with Nine Rings
NASA’s Hubble Space Telescope has captured an extraordinary cosmic bullseye. The massive galaxy LEDA 1313424 is rippling with nine distinct, star-filled rings — far more than astronomers have ever seen in a single galaxy. The cause? A much smaller blue dwarf galaxy that plunged straight through its center like an arrow hitting a target.
Using Hubble, astronomers identified eight visible rings, surpassing the previous record of just two or three rings seen in other galaxies. A ninth ring was confirmed with data from the W. M. Keck Observatory in Hawaii, making this an unprecedented find.
A Lucky Discovery with a Big Impact
“This was a serendipitous discovery,” said Imad Pasha, the lead researcher and a doctoral student at Yale University in New Haven, Connecticut. “I was looking at a ground-based imaging survey and when I saw a galaxy with several clear rings, I was immediately drawn to it. I had to stop to investigate it.” The team later nicknamed the galaxy the “Bullseye.”
Hubble and Keck Observatory’s follow-up observations also helped the researchers prove which galaxy plunged through the center of the Bullseye — a blue dwarf galaxy to its center-left. This relatively tiny interloper traveled like a dart through the core of the Bullseye about 50 million years ago, leaving rings in its wake like ripples in a pond. A thin trail of gas now links the pair, though they are currently separated by 130,000 light-years.
“We’re catching the Bullseye at a very special moment in time,” said Pieter G. van Dokkum, a co-author of the new study and a professor at Yale. “There’s a very narrow window after the impact when a galaxy like this would have so many rings.”
A Rare and Powerful Galactic Event
Galaxies collide or barely miss one another quite frequently on cosmic timescales, but it is extremely rare for one galaxy to dive through the center of another. The blue dwarf galaxy’s straight trajectory through the Bullseye later caused material to move both inward and outward in waves, setting off new regions of star formation.
How big is the Bullseye? Our ” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>Milky Way galaxy is about 100,000 light-years in diameter, and the Bullseye is almost two-and-a-half times larger, at 250,000 light-years across.
The researchers used Hubble’s crisp vision to carefully to pinpoint the location of most of its rings, since many are piled up at the center. “This would have been impossible without Hubble,” Pasha said.
They used Keck Observatory to confirm one more ring. The team suspects a 10th ring also existed, but has faded and is no longer detectable. They estimate it might lie three times farther out than the widest ring in Hubble’s image.
Theoretical Predictions Confirmed
Pasha also found a stunning connection between the Bullseye and a long-established theory: The galaxy’s rings appear to have moved outward almost exactly as predicted by models.
“That theory was developed for the day that someone saw so many rings,” van Dokkum said. “It is immensely gratifying to confirm this long-standing prediction with the Bullseye galaxy.”
If viewed from above, it would be more obvious that the galaxy’s rings aren’t evenly spaced like those on a dart board. Hubble’s image shows the galaxy from a slight angle. “If we were to look down at the galaxy directly, the rings would look circular, with rings bunched up at the center and gradually becoming more spaced out the farther out they are,” Pasha explained.
To visualize how these rings may have formed, think about dropping a pebble into a pond. The first ring ripples out, becoming the widest over time, while others continue to form after it.
The researchers suspect that the first two rings in the Bullseye formed quickly and spread out in wider circles. The formation of additional rings may have been slightly staggered, since the blue dwarf galaxy’s flythrough affected the first rings more significantly.
Individual stars’ orbits were largely undisturbed, though groups of stars did “pile up” to form distinguishable rings over millions of years. The gas, however, was carried outward, and mixed with dust to form new stars, further brightening the Bullseye’s rings.
There’s a lot more research to be done to figure out which stars existed before and after the blue dwarf’s “fly through.” Astronomers will now also be able to improve models showing how the galaxy may continue to evolve over billions of years, including the disappearance of additional rings.
A New Era of Galactic Exploration Awaits
Although this discovery was a chance finding, astronomers can look forward to finding more galaxies like this one soon. “Once NASA’s Nancy Grace Roman Space Telescope begins science operations, interesting objects will pop out much more easily,” van Dokkum explained. “We will learn how rare these spectacular events really are.”
The team’s paper was published on February 4, 2025, in The Astrophysical Journal Letters.
Reference: “The Bullseye: HST, Keck/KCWI, and Dragonfly Characterization of a Giant Nine-ringed Galaxy” by Imad Pasha, Pieter G. van Dokkum, Qing Liu, William P. Bowman, Steven R. Janssens, Michael A. Keim, Chloe Neufeld and Roberto Abraham, 4 February 2025, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/ad9f5c
The Hubble Space Telescope is one of the most important astronomical observatories in history, providing groundbreaking insights into the universe for over three decades. A collaboration between NASA and the European Space Agency (ESA), Hubble orbits Earth, capturing breathtaking images and critical data that have transformed our understanding of space.
Managed by NASA’s Goddard Space Flight Center in Maryland, with mission support from Lockheed Martin Space, Hubble’s operations are conducted by the Space Telescope Science Institute in Baltimore. Since its launch in 1990, Hubble has made countless discoveries, from measuring the expansion of the universe to capturing stunning views of distant galaxies, nebulae, and exoplanets. Despite its age, Hubble continues to be a vital tool for astronomers, pushing the boundaries of space exploration.
