Bullseye! Yale-led team finds a giant galaxy with a record nine rings

A Yale-led research group has discovered “Bullseye,” a galaxy with nine rings that may help astronomers better understand galaxy evolution and dark matter.

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LEDA 1313424, the Bullseye galaxy

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. High-resolution imagery from NASA’s Hubble Space Telescope confirmed eight rings, and data from the W. M. Keck Observatory in Hawaii confirmed a ninth. Hubble and Keck also confirmed which galaxy dove through the Bullseye, creating these rings: the blue dwarf galaxy that sits to its immediate center-left.

Credit: NASA, ESA, Imad Pasha (Yale), Pieter van Dokkum (Yale)
Bullseye! Yale-led team finds a giant galaxy with a record nine rings
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A Yale-led team of astronomers has discovered a cosmic rarity: a super-sized galaxy with nine concentric rings.

Officially known as LEDA 1313424, the “Bullseye” galaxy got its rings about 50 million years ago after a much smaller galaxy collided with its midsection — like a cosmic dart landing dead center in a game of Knockout at the local pub.

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

“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.

Pasha had been looking at a ground-based imaging survey when he initially spotted the galaxy, which had several clear rings. He and his colleagues did more research — identifying eight rings using data from NASA’s Hubble Telescope and a ninth ring using data from the Keck Cosmic Web Imager at the Keck Observatory in Hawaii. The team also used data from the Dragonfly Telephoto Array in New Mexico.

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

Illustration shows the massive galaxy nicknamed the Bullseye face-on

This illustration shows the massive galaxy nicknamed the Bullseye face-on. Dotted circles indicate where each of its rings are, which formed like ripples in a pond after a blue dwarf galaxy (not shown) shot through its core about 50 million years ago. NASA’s Hubble Space Telescope helped researchers carefully pinpoint the location of most of its rings, many of which are piled up at the center. Data from the W. M. Keck Observatory in Hawaii helped the team confirm another ring.

Credit: NASA, ESA, Ralf Crawford (STScI)

Yet Bullseye has more to offer than fancy rings, the researchers say. It provides critical observational data about galaxy formation and the distribution of dark matter — the theorized material thought to constitute most of the matter in the universe.

Pasha said the faint material visible in Bullseye’s outer edges is, in fact, part of a large, faded ring. This indicates that Bullseye is approximately 250,000 light-years in diameter, nearly two-and-a-half times larger than the Milky Way.

The researchers say Bullseye’s immense size suggests that it is evolving from a collisional ring galaxy into a different, larger category of galaxy known as a giant low surface brightness galaxy. “Before this study, no observational evidence existed to support the possibility of this pathway,” Pasha said.

Bullseye may prove similarly helpful in studying the way dark matter is distributed within a galaxy. Pasha noted that rings are one of the few reliable “tracers” for dark matter.

“One can construct dark matter distribution models for this galaxy better than most others,” Pasha said.

Other co-authors of the new study are William Bowman, Michael Keim, and Chloe Neufeld from Yale; Qing Liu and Roberto Abraham from the University of Toronto; and Steven Janssens from Swinburne University in Australia.