The United States National Aeronautics and Space Administration (NASA)’s Hubble Space Telescope has captured an enormous galaxy, LEDA 1313424, with nine concentric rings, resembling a “bullseye” in the universe. This ripple-like multi-ring structure is formed when one galaxy passes through the center of another galaxy, a phenomenon that is extremely rare.
On February 4th, NASA released images of the galaxy taken by the Hubble Space Telescope. This galaxy, named LEDA 1313424, has a diameter of approximately 250,000 light-years, which is 2.5 times the size of the Milky Way. Its appearance of nine concentric rings has earned it the nickname “Bullseye Galaxy.”
NASA indicates that after a “dart” (a smaller blue dwarf galaxy) pierced through the center of LEDA 1313424, it caused the stirring of nine ripple-like rings filled with stars.
The blue dwarf galaxy is located to the left of LEDA 1313424, and it passed through the center of LEDA 1313424 around 50 million years ago, resulting in the multi-ring structure currently observed, much like ripples caused by a stone dropping into a pond.
On the cosmic timescale, galaxy collisions or near-misses are common, but the scenario of one galaxy passing through the center of another galaxy is exceedingly rare. The trajectory of the blue dwarf galaxy passing through the “bullseye” led to material moving inward and outward in wave-like patterns, triggering the formation of new stars.
Despite the two galaxies currently being 130,000 light-years apart, there is a faint trace of gas connecting them.
By using the Hubble Space Telescope, astronomers identified eight rings within LEDA 1313424, more than any telescope has detected in any galaxy before, and they confirmed the ninth ring using data from the W. M. Keck Observatory in Hawaii. Previous observations of other galaxies typically showed only two or three rings.
Imad Pasha, the lead researcher and doctoral student at Yale University, mentioned that their discovery of LEDA 1313424 was purely accidental.
“This was a serendipitous find. I was looking through ground imaging surveys when I saw a galaxy with several distinct rings, and I was immediately intrigued by it. I had to pause and investigate,” he said.
One of the co-authors of the study, Pieter G. van Dokkum, a professor at Yale University, stated, “We captured ‘Bullseye’ at a very special moment. After the collision of those two galaxies, there is only a brief period when LEDA 1313424 would exhibit this many ring structures.”
Pasha explained that if observed from above LEDA 1313424, the spacing of the ring structures within the galaxy would be less uniform than on a dartboard. The Hubble Space Telescope’s image presents the galaxy from a narrow angle.
“If we were directly above the galaxy, the rings would appear more circular. They converge at the center but gradually increase in spacing as you move outward,” Pasha said.
He noted that researchers meticulously determined the positions of most rings within LEDA 1313424 due to the exceptional observation capabilities of the Hubble Space Telescope. “This would not have been possible without the Hubble Space Telescope.”
Researchers initially suspected LEDA 1313424 might have had a tenth ring that has since disappeared and cannot be detected. They estimate that it was three times farther than the widest ring captured in the Hubble Space Telescope’s image.
While the discovery of LEDA 1313424 was accidental, astronomers are optimistic about finding more galaxies like it in the near future. Dokkum stated that once NASA’s Nancy Grace Roman Space Telescope becomes operational, interesting celestial bodies will be easier to spot.
“We will understand how rare these spectacular events truly are,” he said.
NASA announced that the Roman Space Telescope is set to launch in May 2027. With a field of view at least 100 times larger than that of the Hubble Space Telescope, it is expected to observe light from one billion galaxies during its operational lifespan.
Furthermore, the Roman Space Telescope can block starlight, directly observing extrasolar planets and the disk-like structures where planets form. It is anticipated to complete a statistical census of the Milky Way’s planetary system and address fundamental questions in dark energy, extrasolar planets, and infrared astrophysics.
The research findings were published on February 4th in the Astrophysical Journal Letters.