Reviewed by Louis CastelFeb 5 2025
In a study that was published in The Astrophysical Journal Letters, astronomers used Hubble to find eight observable rings—more than any other observatory has ever seen in any galaxy—and used data from Hawaii's W. M. Keck Observatory to confirm a ninth.
LEDA 1313424, aptly nicknamed the Bullseye, is two and a half times the size of our Milky Way and has nine rings — six more than any other known galaxy. Image Credit: NASA, ESA, Imad Pasha (Yale), Pieter van Dokkum (Yale)
A cosmic bullseye has been recorded by NASA's Hubble Space Telescope! The “arrow”—a much smaller blue dwarf galaxy—shot through the center of the enormous galaxy LEDA 1313424, causing it to ripple with nine rings full of stars.
Other galaxies that have been observed in the past have up to two or three rings.
This was a serendipitous discovery. 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".
Imad Pasha, Study Lead Researcher and Doctoral Student, Yale University
Thanks to follow-up studies by Hubble and Keck, astronomers were also able to identify the blue dwarf galaxy to the center-left of the Bullseye as the one that had plunged through its center. About 50 million years ago, this comparatively little intruder darted through the center of the Bullseye, leaving behind rings that resembled pond ripples. Currently separated by 130,000 light-years, the duo is now connected by a narrow trail of gas.
We’re catching the Bullseye at a very special moment in time. There’s a very narrow window after the impact when a galaxy like this would have so many rings.
Pieter G. van Dokkum, Study Co-Author and Professor, Yale University
On cosmic timescales, galaxies collide or barely miss each other rather frequently, but it is quite uncommon for one galaxy to plunge through the core of another. Later, material moved inwards and outward in waves as a result of the blue dwarf galaxy's straight path through the Bullseye, igniting new star-formation zones.
What is the Bullseye's size? At 250,000 light-years across, the Bullseye galaxy is nearly two-and-a-half times larger than the Milky Way galaxy.
Since many of the rings are stacked in the middle, the researchers meticulously located the majority of them using Hubble's sharp vision.
Pasha added, “This would have been impossible without Hubble.”
They used Keck to verify one more ring. The team suspects that a tenth ring existed but has faded and is no longer detectable. They believe that it is three times farther away than the widest ring in Hubble's image.
A One-to-One Match with Predictions
Pasha also discovered an astonishing link between the Bullseye and a long-held theory: the galaxy's rings appear to have shifted outward almost exactly predicted by models.
“That theory was developed for the day that someone saw so many rings. It is immensely gratifying to confirm this long-standing prediction with the Bullseye galaxy,” van Dokkum stated.
When viewed from above, the galaxy's rings are not regularly spaced. Hubble's image captures the galaxy at 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.
Consider tossing a stone into a pond to get an idea of how these rings would have developed. Over time, the first ring spreads out and widens, and others keep forming after it.
The first two rings in the Bullseye are believed to have developed rapidly and dispersed into bigger circles. Given that the flythrough of the blue dwarf galaxy had a greater impact on the initial rings, the creation of the other rings might have been somewhat delayed.
The orbits of individual stars were mainly unaffected, but after millions of years, clusters of stars did "pile up" to form recognizable rings. However, the gas was carried outward and combined with dust to create other stars, which made the Bullseye's rings even brighter.
To determine which stars existed before and after the blue dwarf's "fly through," much more investigation is needed. Additionally, astronomers will now be able to refine models that depict how the galaxy might continue to change over billions of years, including the loss of more rings.
Astronomers anticipate discovering additional galaxies similar to this one in the near future, despite the accidental nature of this discovery.
van Dokkum added, “Once NASA’s Nancy Grace Roman Space Telescope begins science operations, interesting objects will pop out much more easily. We will learn how rare these spectacular events really are.”
The Hubble Space Telescope has been in operation for more than three decades and continues to make groundbreaking discoveries that impact our fundamental understanding of the universe. NASA and ESA collaborated on the Hubble Space Telescope project. NASA's Goddard Space Flight Center in Greenbelt, Maryland, oversees the telescope and mission operations.
Journal Reference:
Pasha, I., et. al. (2025) The Bullseye: HST, Keck/KCWI, and Dragonfly Characterization of a Giant Nine-ringed Galaxy. The Astrophysical Journal Letters. doi.org/10.3847/2041-8213/ad9f5c