Top 10 Largest Galaxies Ever Discovered

#1: Alcyoneus Galaxy (~16.3 million light-years wide)

Discovered relatively recently, Alcyoneus is a true galactic behemoth, stretching approximately 16.3 million light-years from tip to tip, making it the largest known galaxy in the observable universe. What’s truly fascinating is that its central host galaxy is fairly ordinary in size—just another elliptical in a modest cluster. But Alcyoneus earns its titanic stature from its colossal radio lobes, which extend light-years beyond the visible portion of the galaxy. These lobes are fueled by jets emanating from the supermassive black hole at its center, spewing plasma at near-light speeds and interacting with intergalactic medium. Detected via the LOFAR radio telescope, Alcyoneus defies the conventional wisdom that only dense galaxy clusters harbor the largest radio galaxies. It’s a spectacular reminder that even in less populated corners of the cosmos, nature can scale the unimaginable. Alcyoneus’s ghostly radio footprint tells a story billions of years in the making—a slow, symphonic expansion of energy into the fabric of spacetime.

#2: IC 1101 (~3.9 million light-years wide)

Located in the Abell 2029 galaxy cluster, IC 1101 was long considered the reigning champion among galaxies, with an estimated diameter of 3.9 million light-years—nearly 40 times the width of the Milky Way. Situated about 1.04 billion light-years from Earth, this massive elliptical galaxy contains over 100 trillion stars, and its central region is cloaked in a yellow glow from ancient, aging suns. At its heart lies one of the most massive black holes ever estimated, possibly weighing over 40 billion times the mass of our sun. IC 1101 likely grew to its immense size through a process known as galactic cannibalism—devouring smaller galaxies over billions of years. Its history is etched into its bloated shape and the vast population of globular clusters surrounding it like galactic breadcrumbs. For years, IC 1101 was the symbol of cosmic excess—until radio observations brought even larger giants like Alcyoneus into the limelight.

#3: Hercules A (~3.3 million light-years wide)

What makes Hercules A especially dramatic isn’t just its size—spanning roughly 3.3 million light-years—but the violent activity emanating from its core. Situated about 2.1 billion light-years away, this elliptical galaxy is host to a supermassive black hole that’s roughly 1,000 times more massive than the one in our Milky Way. The real spectacle lies in its twin radio jets, which blast out energetic material for millions of light-years on either side. These jets carve vast cavities into the intergalactic medium, heating and displacing matter like invisible tidal waves. Discovered using both visible-light and radio astronomy, Hercules A is an extreme case of a galaxy whose beauty is both awe-inspiring and slightly terrifying. You wouldn’t want to be anywhere near the heart of this monster. Its scale and power are so intense, astronomers often use it to model how galactic nuclei influence surrounding space. Hercules A might be a silent sentinel in the night sky, but it tells a tale of high-energy chaos on a truly galactic scale.

#4: ESO 146-IG 005 (~2.6 million light-years wide)

Hidden in the southern constellation of Indus, ESO 146-IG 005 spans over 2.6 million light-years and is located nearly 1.1 billion light-years from Earth. It’s a peculiar system known as a “fossil group”—a dominant galaxy that appears to have consumed most of its neighbors. What remains is a faint halo of stars and gas spread out over a massive volume of space. What makes ESO 146-IG 005 particularly compelling is that its mass-to-light ratio is heavily skewed, implying the overwhelming presence of dark matter. Observations from the Hubble Space Telescope suggest it formed early in cosmic history and has remained relatively undisturbed since then. In some ways, it’s a relic of galactic evolution—a time capsule from the era when galaxy formation was at its peak. The galaxy’s understated visual presence hides an extraordinary structure rich in complexity and mystery.

#5: Phoenix A (~2.4 million light-years wide)

Located in the Phoenix Cluster—one of the most massive galaxy clusters in the known universe—Phoenix A is a central elliptical galaxy that stretches over 2.4 million light-years in diameter. At the heart of this massive galaxy is an active galactic nucleus that releases powerful jets, heating nearby gas and slowing down star formation. Despite this feedback, Phoenix A still manages to produce stars at an astonishing rate—around 500 solar masses per year, one of the highest ever recorded. This creates a fascinating contradiction: a galaxy actively cooling and forming stars while simultaneously emitting vast quantities of energy. With the help of X-ray and radio telescopes, astronomers have been able to study how this galactic ecosystem regulates itself, offering clues to the behavior of other massive galaxies in the early universe. Phoenix A is both a powerhouse and a puzzle, blending ancient structure with young, fiery activity.

#6: NGC 262 (~2.1 million light-years wide)

NGC 262 might not be a household name, but in astronomical circles, it’s considered a standout due to its size and structure. Estimated at around 2.1 million light-years across, this giant spiral galaxy is located roughly 280 million light-years from Earth in the constellation Andromeda—not to be confused with the Andromeda Galaxy itself. NGC 262 is particularly intriguing for being a type-Seyfert galaxy, meaning its nucleus is unusually bright due to energetic emissions from the central supermassive black hole. What separates NGC 262 from other large spirals is its low surface brightness; despite its vast scale, its luminosity is relatively modest compared to its mass. This suggests that the galaxy might contain an abundance of dark matter or perhaps an aging population of stars. The arms of the galaxy are long and wispy, faintly illuminated with sparse star formation, and they wind around a prominent, dense bulge—like silk ribbons fluttering around a glowing core. For astronomers, NGC 262 offers a haunting look into the quieter side of galaxy evolution.

#7: UGC 2885 (~1.8 million light-years wide)

Dubbed “Rubin’s Galaxy” in honor of pioneering astronomer Vera Rubin, UGC 2885 is the largest spiral galaxy ever discovered. Located in the constellation Perseus and approximately 232 million light-years away, this spiral behemoth spans a staggering 1.8 million light-years, nearly 20 times the size of our Milky Way. Its disk is a classic example of graceful galactic structure—broad arms spiraling outward with remarkable symmetry, filled with regions of active star formation. Despite its size, UGC 2885 is surprisingly quiet; it shows none of the dramatic features typical of galaxies involved in major collisions. That has led scientists to believe that UGC 2885 grew steadily over billions of years, feeding off smaller galaxies without much disruption. The galaxy contains an estimated 1 trillion stars, and observations have revealed a calm rotation curve, suggesting it’s embedded in an enormous halo of dark matter. Rubin’s Galaxy isn’t just big—it’s beautifully balanced and scientifically vital to understanding galactic stability on cosmic scales.

#8: Comet Galaxy (~1.4 million light-years long)

Residing in the Abell 2667 cluster about 3.2 billion light-years away, the Comet Galaxy earns its name from its remarkable appearance. Measuring around 1.4 million light-years in length, this galaxy is being torn apart as it plunges through the dense cluster environment. The result is a stream of stars, gas, and dark matter trailing behind like the tail of a comet. As the Comet Galaxy speeds through the intracluster medium at nearly 2 million miles per hour, it’s subjected to intense gravitational forces that rip material from its outer edges—a process known as ram-pressure stripping. Hubble Space Telescope images captured this moment of galactic trauma in vivid detail, making the Comet Galaxy both a visual marvel and a prime case study of galactic destruction. This fleeting yet monumental phase in a galaxy’s life provides insight into how environment affects evolution, especially in densely packed clusters. Though it’s being pulled apart, the Comet Galaxy teaches us more with its collapse than many galaxies do in their prime.

#9: Malin 1 (~1.3 million light-years wide)

Malin 1 is a galaxy that redefined what astronomers thought was possible in terms of spiral structure. Located approximately 1.2 billion light-years from Earth in the constellation Coma Berenices, Malin 1 measures an astonishing 1.3 million light-years in diameter. What makes it particularly unique is its classification as a giant low-surface-brightness (LSB) spiral galaxy. In simpler terms, it’s massive but faint, with sprawling arms that emit just a whisper of light. Discovered in the 1980s through photographic plates, Malin 1 wasn’t even recognized for its full size until advanced digital imaging techniques revealed the true scope of its outer disk. Despite its size, it has relatively little star formation, suggesting a quiet, isolated existence. Malin 1 seems to have evolved without many galactic mergers or violent events, preserving its diffuse, ghostly structure. It’s a cosmic phantom—enormous yet nearly invisible to conventional observation. For scientists studying the extremes of galaxy formation, Malin 1 remains one of the most enigmatic specimens in the universe.

#10: NGC 6872 (~1.2 million light-years wide)

Nicknamed the “Condor Galaxy,” NGC 6872 is a barred spiral galaxy with incredible wingspan—estimated at over 1.2 million light-years. Located about 212 million light-years from Earth in the constellation Pavo, NGC 6872 is notable not just for its sheer size, but also for its striking symmetry and interactions. The galaxy owes its massive spiral arms in part to a nearby galactic neighbor, IC 4970, which passed close to it about 130 million years ago. This gravitational encounter stretched NGC 6872’s arms to unprecedented lengths, triggering waves of star formation along its outer disk. Observations in ultraviolet light show bright regions peppered across its arms—stellar nurseries ignited by the tug-of-war between galaxies. NGC 6872 continues to fascinate astronomers because it’s a rare example of how galactic collisions can enhance, rather than destroy, spiral structures. Despite the drama of its past, it remains one of the most elegant examples of large-scale spiral architecture in the sky.

These ten galaxies aren’t just enormous—they’re profoundly important to our understanding of how matter, energy, and time interweave in the cosmic ballet. From radio-lobe giants like Alcyoneus to ghostly phantoms like Malin 1, each one provides a unique window into the life and evolution of galaxies at the largest scales. Their sizes stretch our imagination, their stories deepen our curiosity, and their diversity reflects the incredible creativity of the universe. Whether through mergers, collisions, slow growth, or cosmic isolation, these galaxies have earned their place among the giants—and in the annals of astronomy.