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Gemini North Captures Starburst Galaxy Blazing Bright With Newly Forming Stars

June 25, 2024

Irregular galaxy NGC 4449 exhibits explosive rate of star formation activity due in part to ongoing mergers with nearby dwarf galaxies

A festive array of bright pinks and blues makes for a remarkable sight in this image captured with the Gemini North telescope, one half of the International Gemini Observatory. Resembling a cloud of cosmic confetti, this image is being released in celebration of Gemini North’s 25th anniversary. NGC 4449 is a prime example of starburst activity caused by the interacting and mingling of galaxies as it slowly absorbs its smaller galactic neighbors.

Much of the visible matter in the Universe, the matter that makes up stars, planets — and us — is made inside stars as they complete their cycle of birth, life, and death. They are born from clouds of gas and dust, and when they die their remains are recycled back into the interstellar medium to be used as fuel for the next generation of stars. And in a not-so-distant corner of the Universe, 13 million light-years away in the constellation Canes Venatici, the beginning of this cycle is unfolding at an exceptional rate.

NGC 4449, also known as Caldwell 21, appears to be putting on a cosmic fireworks show in this image, captured with the Gemini North telescope, one half of the International Gemini Observatory, which is supported in part by the U.S. National Science Foundation and operated by NSF NOIRLab. The galaxy’s billowing red clouds and sparkling blue veil are lighting up the sky with the colors of newly forming stars. It’s classified as an irregular Magellanic-type galaxy, reflecting its loose spiral structure and close resemblance to the Large Magellanic Cloud — the prototype of Magellanic galaxies.

Stars have been actively forming within NGC 4449 for several billion years, but currently it is pumping out new stars at a much higher rate than in the past. This unusually explosive and intense star formation activity qualifies it as a starburst galaxy. While starbursts usually occur in the central regions of galaxies, NGC 4449’s star formation is more widespread, evidenced by the fact that the youngest stars are both in the nucleus and in streams surrounding the galaxy.

This ‘global’ starburst activity resembles the Universe’s earliest star-forming galaxies, which grew by merging with and accreting smaller stellar systems. And like its galactic predecessors, NGC 4449’s rapid star formation was likely ignited by interactions with neighboring galaxies. As a member of the M94 Group of galaxies — one of the closest galaxy groups to the Local Group, which hosts the Milky Way — NGC 4449 lies in close proximity to a handful of surrounding smaller galaxies. Astronomers have found evidence of interactions between NGC 4449 and at least two of these satellite galaxies.

One is a very dim dwarf galaxy that is actively being absorbed, as evidenced by a diffuse stream of stars extending to one side of NGC 4449. This ‘stealth’ merger is nearly undetectable by visual inspection owing to its diffuse nature and low stellar mass. However, it possesses a large amount of dark matter, meaning its presence can be detected by the substantial gravitational influence it has on NGC 4449. The other object that provides hints of a past merger is a massive globular star cluster embedded within the outer halo of NGC 4449. This cluster is thought by astronomers to be the surviving nucleus of a former gas-rich satellite galaxy now in the process of being absorbed by NGC 4449.

As NGC 4449 interacts with and absorbs its smaller galactic companions, the tidal interactions between the galaxies compress and shock the gas. The glowing red regions scattered across this image showcase this process, indicating an abundance of ionized hydrogen — a telltale sign of ongoing star formation. A plethora of hot, young blue star clusters are emerging from the galactic ovens, fueled by the dark filaments of cosmic dust lacing throughout the galaxy. At the current rate, the gas supply that feeds NGC 4449’s production of stars will only last for another billion years or so.

This image is being released today in celebration of the Gemini North telescope’s 25th anniversary. On 25 June 1999 a dedication ceremony was held on Maunakea, Hawai‘i, to unveil the new world-class 8.1-meter telescope and reveal its first-light images, which at the time were some of the sharpest infrared images ever obtained by a ground-based telescope. Over the past two and a half decades Gemini North’s large mirror, powerful suite of instruments and advanced adaptive optics have allowed astronomers to peer further and further into the cosmos. From capturing the first direct image of a multi-planet system to testing Einstein’s general theory of relativity — which helped astronomers earn the 2020 Nobel Prize — Gemini North has contributed greatly to humanity’s understanding of the Universe.

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NSF NOIRLab (U.S. National Science Foundation National Optical-Infrared Astronomy Research Laboratory), the U.S. center for ground-based optical-infrared astronomy, operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), Kitt Peak National Observatory (KPNO), Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and Vera C. Rubin Observatory (operated in cooperation with the Department of Energy’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona. The astronomical community is honored to have the opportunity to conduct astronomical research on I’oligam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, 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.

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