From The NSF NOIRLab NOAO Gemini Observatory: “‘Taffy Galaxies’ Collide and Leave Behind Bridge of Star-Forming Material” 

Gemini Observatory

From The NSF NOIRLab NOAO Gemini Observatory

Josie Fenske

The Gemini North telescope, one half of the International Gemini Observatory, operated by NSF’s NOIRLab, captured this dazzling image of UGC 12914 and UGC 12915, which are nicknamed the Taffy Galaxies. Their twisted shape is the result of a head-on collision that occurred about 25 million years prior to their appearance in this image. A bridge of highly turbulent gas devoid of significant star formation spans the gap between the two galaxies.

Galaxy collisions are transformative events, largely responsible for driving the evolution of the Universe. The mixing and mingling of stellar material is an incredibly dynamic process that can lead to the formation of molecular clouds populated with newly forming stars. But, a head-on collision between the two galaxies UGC 12914 (left) and UGC 12915 (right) 25–30 million years ago appears to have resulted in a different kind of structure — a bridge of highly turbulent material spanning the two galaxies. Though this intergalactic bridge is teeming with star-forming material, its turbulent nature is suppressing star formation.

This pair of galaxies, nicknamed the Taffy Galaxies, is located about 180 million light-years away in the direction of the constellation Pegasus.

This new image, captured with Gemini North [1], one half of the International Gemini Observatory, operated by NSF’s NOIRLab, showcases the fascinating feature that gave them their name. A tenuous bridge composed of narrow molecular filaments, shown in brown, and clumps of hydrogen gas, shown in red, can be seen between the two galaxies. Its complex web structure resembles taffy being stretched as the pair slowly separates.

Galaxy collisions can happen out of a variety of different scenarios, often involving a larger galaxy and a smaller satellite galaxy. As they drift near one another, the satellite galaxy can attract one of the larger galaxy’s primary spiral arms, pulling it out of its orbit. Or the satellite galaxy can actually intersect with the larger galaxy, causing significant distortions to its own structure. In other cases, a collision can lead to a merger if neither member has enough momentum to continue on after colliding. In all these scenarios, stellar material from both galaxies mixes through a gradual combining and redistribution of gas, like two puddles of liquid that are slowly bleeding into each other. The resulting collecting and compression of the gas can then trigger star formation.

A head-on collision, however, would be more like pouring liquid from two separate cups into a shared bowl. When the Taffy Galaxies’ collided, their galactic disks and gaseous components smashed right into each other. This resulted in a massive injection of energy into the gas, causing it to become highly turbulent. As the pair emerged from their collision, high-velocity gas was pulled from each galaxy, creating a massive gas bridge between them. The turbulence of the stellar material throughout the bridge is now prohibiting the collection and compression of gas that are required to form new stars.

The Gemini North observations of this object were led by Analía Smith Castelli, an astronomer with the Instituto de Astrofísica de La Plata in Argentina. Argentina is one of the partners in the International Gemini Observatory.


[1] The data for this image were acquired before the Gemini North primary mirror was taken offline for repairs.

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Gemini Observatory

National Science Foundation’s NOIRLab National Optical-Infrared Astronomy Research Laboratory, the US center for ground-based optical-infrared astronomy, operates the international Gemini Observatory (a facility of NSF, NRC–Canada, Gemini Argentina |, ANID–Chile, Ministry of Science, Technology, Innovation and Communications [Ministério da Ciência, Tecnolgia, Inovação e Comunicações](BR), and Korea Astronomy and Space Science Institute[알림사항])(KR)

National Science Foundation NOIRLab’s Gemini North Frederick C Gillett telescope at Mauna Kea Observatory Hawai’i, Altitude 4,213 m (13,822 ft).

Mauna Kea Observatories Hawai’i, altitude 4,213 m (13,822 ft).

NSF NOIRLab NOAO Gemini South telescope on the summit of Cerro Pachón at an altitude of 7200 feet. There are currently two telescopes commissioned on Cerro Pachón, Gemini South and the Southern Astrophysical Research Telescope. A third, the Vera C. Rubin Observatory, is under construction.

NSF NOIRLab NOAO Cerro Tololo Inter-American Observatory(CL) approximately 80 km to the East of La Serena, Chile, at an altitude of 2200 meters.

Gemini’s mission is to advance our knowledge of the Universe by providing the international Gemini Community with forefront access to the entire sky.

The NSF NOIRLab Gemini Observatory is an international collaboration with two identical 8-meter telescopes. The Frederick C. Gillett Gemini Telescope is located on Mauna Kea, Hawai’i (Gemini North) and the other telescope, Gemini South, on Cerro Pachón in central Chile); together the twin telescopes provide full coverage over both hemispheres of the sky. The telescopes incorporate technologies that allow large, relatively thin mirrors, under active control, to collect and focus both visible and infrared radiation from space.

The Gemini Observatory provides the astronomical communities in six partner countries with state-of-the-art astronomical facilities that allocate observing time in proportion to each country’s contribution. In addition to financial support, each country also contributes significant scientific and technical resources. The national research agencies that form the Gemini partnership include: the National Science Foundation, the Canadian National Research Council, the Chilean Comisión Nacional de Investigación Cientifica y Tecnológica, the Australian Research Council, the Argentinean Ministerio de Ciencia, Tecnología e Innovación Productiva, and the Brazilian Ministério da Ciência, Tecnologia e Inovação. The observatory is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the NSF. The NSF also serves as the executive agency for the international partnership.

National Science Foundation’s NOIRLab (National Optical-Infrared Astronomy Research Laboratory ), the center for ground-based optical-infrared astronomy, operates the international Gemini Observatory (a facility of NSF, National Research Council Canada (CA), Agancia Nacional de IInvestigacion y Desarrollo (CL), Ministry of Science, Technology and Innovation [Ministério da Ciência, Tecnologia e Inovações] (BR), Ministry of Science, Technology and Innovation | Argentina.gob.Ministerio de Ciencia, Tecnología e Innovación | Argentina.gob.(AR), and Korea Astronomy and Space Science Institute[알림사항](KR), Kitt Peak National Observatory (KPNO) , NSF NOAO Cerro Tololo Inter-American Observatory (CL), the NOAO Community Science and Data Center (CSDC), and Vera C. Rubin Observatory in cooperation with DOE’s SLAC National Accelerator Laboratory ).

It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with National Science Foundation and is headquartered in Tucson, Arizona.
The astronomical community is honored to have the opportunity to conduct astronomical research on Iolkam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawaiʻi, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence that these sites have to the Tohono O’odham Nation, to the Native Hawaiian community, and to the local communities in Chile, respectively.