Yale astronomers have announced the discovery of a galaxy with nine concentric rings—the most rings ever seen in a single galaxy. At more than twice the diameter of our Milky Way, it stretches approximately 250,000 light-years across. Dubbed the “Bullseye,” this record-breaking system is officially named LEDA 1313424 and it could hold some clues regarding dark matter.

Blame a collision for the rings

The research team said these rings likely formed when a smaller galaxy shot through the heart of the Bullseye galaxy roughly 50 million years ago.

“The collision triggered the creation of nine beautiful, symmetrical rings, which are now expanding outwards, carrying gas away from the center,” said lead author Imad Pasha, a Yale doctoral student in astronomy and the principal investigator of the new study, appearing in The Astrophysical Journal Letters.

It’s not that uncommon for galaxies to have rings, but most have just one or two. In some well-known cases, such as the Cartwheel Galaxy, a head-on collision also produced multiple concentric features—but nowhere near the amount seen in Bullseye.

Astronomers say catching all nine rings so clearly at once is exceptionally rare, especially because such rings are not long-lived on the cosmic scale. Collisional rings form and fade in just a few hundred million years, a fleeting instant in the life of a galaxy.

“We’re catching the Bullseye at a very special moment in time,” said Pieter van Dokkum, Yale’s Sol Goldman Family Professor of Astronomy and Physics and a co-author on the study. “There’s a very narrow window after the impact when a galaxy like this would have so many rings.”

Researchers explain that the Bullseye galaxy was quiet until the smaller “impactor” galaxy—a blue dwarf observed near Bullseye—plunged through its midsection. This violent encounter sent waves of compressed gas and dust rolling outwards. As those waves moved through the galaxy’s disk, they triggered bursts of star formation, each new wave appearing as a ring in telescope images. Over time, outer rings expand and fade, while new rings form closer to the core.

“This galaxy breaks the record for most rings discovered in this type of system, a confluence of catching it at a lucky time, at a lucky orientation, and arising from a lucky collision configuration,” Pasha said.

The team pieced together this cosmic enigma through a combination of powerful telescopes. NASA’s Hubble Space Telescope was used to closely examine the Bullseye, confirming eight rings with crisp, high-resolution images. Meanwhile, the W. M. Keck Observatory in Hawaii used its Cosmic Web Imager to detect a dim, ninth ring and confirm that the dwarf galaxy has the proper motion and disturbed gas to be the culprit that created the Bullseye’s rings. Finally, the Dragonfly Telephoto Array—an innovative system of camera lenses designed to see very faint structures—captured low surface brightness features in the outer edges of Bullseye, revealing just how extensive the entire system really is.

Hidden Giants and Dark Matter

Beyond the immediate fascination with nine bright circles, astronomers say that Bullseye represents a crucial example of how galaxies may grow into so-called giant low surface brightness galaxies (GLSBs). These GLSBs are rare, massive galaxies with faint outer regions—so faint they often go unnoticed by surveys focusing on brighter structures.

“Before this study, no observational evidence existed to support the possibility of this pathway,” said Pasha, commenting on the idea that a typical spiral galaxy can be forcefully expanded by a collision and eventually turn into a far larger and dimmer system.

According to previous computer models, the Cartwheel Galaxy might have evolved similarly after enough time had passed—but no one had ever directly observed a ring galaxy at the brink of such a transformation.

The Bullseye’s immense size and exceptionally large store of neutral hydrogen gas point to an unusual amount of raw material for future star formation. Coupled with what astronomers already know about GLSBs, it provides a strong link between ring collisions and these massive, faint behemoths.

There is another reason why Bullseye has scientists buzzing: it offers a pristine look at how dark matter might be distributed inside galaxies. Dark matter is an invisible component thought to make up most of the universe’s matter. Rings expand as waves within the galaxy’s gravitational field, so measuring their positions, sizes, and speeds can help researchers map how matter—both visible and dark—is distributed.

In many ways, Bullseye provides a controlled experiment. Typically, galaxies are chaotic systems with many competing forces, making isolating dark matter’s role challenging. But because a single event forms Bullseye’s rings—one galaxy plunging through another—the ripples act like cosmic test waves, giving astronomers a clearer way to probe the underlying structure of matter, both seen and unseen.

Bullseye’s rings will not last forever. Astronomers anticipate that within a few hundred million years, the distinct circles may merge into a more diffuse disk or spiral arms, leaving only subtle hints of the violent collision. For now, though, the discovery offers an unparalleled opportunity: a dramatic, short-lived phase that reveals how galaxies collide, evolve, and sometimes transform into unexpectedly giant forms.

“We’ve effectively caught Bullseye in the act of becoming something else,” Pasha said. “It’s a glimpse of cosmic evolution that we rarely see so clearly.”