Prior to the pioneering 2025 work that discovered the Bullseye galaxy, showcased here, no galaxy had more than three concentric rings ever discovered within it. The Bullseye galaxy has at least 9, and potentially more that have faded away, due to a galactic collision that occurred a scant ~50 million years ago. (Credit: NASA, ESA, Imad Pasha (Yale), Pieter van Dokkum (Yale))
Ring galaxies are rare, but we think we know how they form. A new, early-stage version, the Bullseye galaxy, provides a new testing ground.
Across the Universe, galaxies come in four major types.
At a level of 36x zoom, Euclid’s first mosaic contains the distant but abundant galaxy cluster Abell 3381, which features a line of bright galaxies similar to Markarian’s chain in the Virgo cluster. Spirals and ellipticals are the most common type of galaxy, with many others that are interacting forming transient, irregular, peculiar shapes. However, rarely galaxies will also appear with a ring-like configuration, such as the one at the top, about 25% of the way from the right image edge. (Credit: ESA/Euclid/Euclid Consortium/NASA, CEA Paris-Saclay; Processing: J.-C. Cuillandre, E. Bertin, G. Anselmi)
Spiral and ellipticals describe most common, normal galaxies.
The lensed galaxies shown at the center of this image appear as though they’re being stretched and pulled apart, similar to the chromosome pairs that align and separate during cellular mitosis. However, this is only an optical illusion caused by the gravitational lensing effects of the massive foreground galaxy cluster: El Gordo. These are simply background galaxies whose light is distorted by the gravitational lens. Both spirals and ellipticals are richly represented within (and behind) most galaxy clusters. (Credit: Jose M. Diego (IFCA), Brenda Frye (University of Arizona), Patrick Kamieneski (ASU), Tim Carleton (ASU), Rogier Windhorst (ASU); Processing: Alyssa Pagan (STScI), Jake Summers (ASU), Jordan C. J. D’Silva (UWA), Anton M. Koekemoer (STScI), Aaron Robotham (UWA), Rogier Windhorst (ASU))
Many small or interacting galaxies become irregularly shaped.
The low-mass, dusty, irregular galaxy NGC 3077 is actively forming new stars, has a very blue center, and has a hydrogen gas bridge connecting it to the nearby, more massive M81. As one of 34 galaxies in the M81 Group, it’s an example of the most common type of galaxy in the Universe: much smaller and lower in mass, but far more numerous, than galaxies like our Milky Way. The young stars within it have formed from gas reservoirs still present within this galaxy, indicating an “alive” galaxy. (Credit: ESA/Hubble and NASA)
This X-ray/optical composite image shows the ring galaxy AM 0644–741 along with a wide-field view of its surroundings. Below and to the left of this ring galaxy is a gas-poor ellipsoidal galaxy that may have punched through the ringed galaxy a few hundred million years earlier. The subsequent formation and evolution of a ring of new stars would be expected from the propagation of gas away from the center, like ripples in a pond. (Credit: X-ray: NASA/CXC/INAF/A. Wolter et al; Optical: NASA/STScI)
Only 1-in-10,000 galaxies are rings: defined by circular collections of stars beyond the main galactic body.
