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Scientists Discover Way to Send Information into Black Holes Without Using Energy

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Astronomers Finally Reveal the True Size of the Largest Galaxy Ever Discovered — And It's Even More Enormous Than We Thought

For decades, astronomers have known about IC 1101, a gigantic galaxy located at the center of a distant galaxy cluster. It has long been considered one of the biggest galaxies ever discovered. However, scientists faced one major challenge—they could not accurately determine where the galaxy actually ended.

Now, thanks to the deepest images ever captured of IC 1101, astronomers have finally identified its true outer boundary. Their findings confirm that IC 1101 is the largest known galaxy in the universe, stretching an incredible 1.7 million light-years across. The discovery also reveals that the galaxy contains around 3.4 trillion times the mass of our Sun in stars alone, making it one of the most massive stellar systems ever observed.

Even more exciting, researchers found signs that this cosmic giant is still growing today, continuing to absorb smaller galaxies after billions of years.

The study, published as a preprint on the arXiv server on July 16, provides one of the clearest views yet of how the universe's biggest galaxies evolve.

A Giant Among Giants

Galaxies come in many different shapes and sizes. Some contain only a few million stars, while others hold hundreds of billions.

Our own Milky Way is considered a large spiral galaxy. It stretches roughly 100,000 light-years across (around 30 kiloparsecs) and contains hundreds of billions of stars.

IC 1101 belongs to a very different category known as a Brightest Cluster Galaxy (BCG).

These galaxies sit at the very center of massive galaxy clusters, where thousands of galaxies are bound together by gravity. Because they occupy the middle of these crowded environments, they slowly grow over billions of years by pulling in and merging with nearby galaxies.

Every merger adds more stars, gas, and dark matter, gradually transforming these galaxies into enormous cosmic structures.

Scientists believe IC 1101 has been growing this way for billions of years, making it one of the most extreme examples of galaxy evolution.

Why Measuring Its Size Was So Difficult

Although astronomers have studied IC 1101 for years, measuring its actual size turned out to be surprisingly challenging.

Unlike galaxies with clearly defined edges, IC 1101 has an enormous and extremely faint outer halo made of stars stripped from smaller galaxies during past mergers.

This halo blends almost seamlessly into the surrounding intracluster light—the faint glow produced by stars floating freely between galaxies inside the cluster.

As a result, scientists struggled to determine exactly where the galaxy stopped and where the surrounding galaxy cluster began.

Previous estimates suggested the galaxy extended as far as 607 kiloparsecs, but those measurements were uncertain because the galaxy's faint outer regions were difficult to separate from surrounding light.

To solve this problem, astronomers needed much deeper observations and better image-processing techniques than ever before.

Capturing the Deepest Images Ever Taken

The international research team, led by Carlos Marrero-de la Rosa from the Instituto de Astrofísica de Canarias, focused their attention on IC 1101 using the Wide Field Camera mounted on the Isaac Newton Telescope (INT).

Their goal was simple—but extremely difficult.

They wanted to detect the galaxy's faintest stars and identify its true outer edge.

However, another obstacle stood in the way.

Images taken by telescopes are often affected by scattered light from bright foreground stars located much closer to Earth.

This scattered light spreads across astronomical images like a thin fog, hiding the very faint structures researchers are trying to observe.

For galaxies as enormous and faint as IC 1101, this unwanted glow can completely mask the outer regions.

Removing Light Pollution from Space Images

To overcome this problem, the researchers created a highly detailed model of how light spreads inside the telescope.

They studied dozens of calibration stars with different brightness levels to understand exactly how each star's light was scattered by the telescope's optics.

Using this model, they carefully removed the unwanted glow from more than 250 foreground stars, one by one.

This painstaking process dramatically improved the final image and revealed structures that had previously remained hidden.

Once the scattered light was removed, the team could clearly trace how the brightness of IC 1101 changed from its center toward its outer regions.

This allowed them to identify the galaxy's true edge for the first time.

The Largest Galaxy Ever Measured

The researchers found that IC 1101 has an outer radius of approximately 260 kiloparsecs.

That means its total diameter measures about 520 kiloparsecs, or roughly 1.7 million light-years.

This officially confirms IC 1101 as the largest known galaxy ever measured.

To understand just how enormous that is, consider our own galaxy.

The Milky Way spans only about 30 kiloparsecs.

That means IC 1101 is roughly 17 times wider than the Milky Way.

If the Milky Way were enlarged to the size of a small coin, IC 1101 would be comparable to a large dinner plate.

Its size is almost difficult to imagine.

A Truly Astonishing Mass

Size alone is not what makes IC 1101 extraordinary.

Its mass is equally impressive.

The team estimates that the galaxy contains around 3.4 trillion solar masses in stars.

A solar mass is simply the mass of our Sun.

This means IC 1101 holds as much stellar material as 3.4 trillion Suns.

To put that into perspective, the entire Milky Way, including its invisible dark matter halo, is estimated to have a total mass of only 1 to 1.5 trillion solar masses.

In other words, the stars inside IC 1101 alone outweigh everything in our galaxy—including all of its dark matter.

Few galaxies in the known universe come close to matching such enormous scale.

Hidden Clues Around the Galaxy

The researchers also discovered something unexpected beyond the galaxy's newly identified edge.

They detected eight extremely faint, asymmetric stellar structures surrounding IC 1101.

These enormous streams of stars likely formed when smaller galaxies were pulled apart by gravity during previous mergers.

Some of these structures line up with unusual disturbances observed in X-ray images of the hot gas filling the surrounding galaxy cluster.

Astronomers describe these disturbances as "sloshing," where giant clouds of hot gas continue moving long after a massive collision.

These matching patterns provide strong evidence that IC 1101 has experienced major interactions with other galaxies and galaxy groups.

Rather than being a quiet, stable system, the galaxy is still undergoing dramatic changes.

Still Growing After Billions of Years

One of the study's most exciting conclusions is that IC 1101 is still growing.

The faint outer structures suggest that the galaxy continues to absorb stars and smaller galaxies from its surroundings.

Astronomers call this process ongoing mass assembly.

Instead of reaching a final size billions of years ago, IC 1101 is continuing to evolve as gravity pulls more material toward its center.

Earlier X-ray studies had already suggested that the galaxy cluster experienced a major collision around 2 to 3 billion years ago.

The new observations support that idea, showing lingering signs of those ancient cosmic encounters.

Every future merger could make IC 1101 even larger than it is today.

Why This Discovery Matters

Finding the true size of IC 1101 is about much more than setting a cosmic record.

The galaxy serves as a natural laboratory for studying how the universe builds its largest structures.

By understanding where IC 1101 ends and examining the faint streams of stars around it, astronomers can reconstruct billions of years of galaxy mergers and interactions.

The improved imaging techniques developed for this research may also help scientists study other giant galaxies whose faint outer regions have remained hidden until now.

As telescopes become even more powerful, future observations may uncover galaxies that rival or even surpass IC 1101.

For now, however, IC 1101 remains the undisputed giant of the known universe—a galaxy stretching 1.7 million light-years across, containing trillions of stars, and continuing to grow through the slow but relentless pull of gravity.

The discovery reminds us that the universe is still full of surprises, and even objects we've known about for decades can reveal astonishing new secrets when viewed with better technology and deeper observations.

Reference: Carlos Marrero-de la Rosa et al, How large can galaxies be? Ultra-deep imaging of IC 1101, the most extended known galaxy, arXiv (2026). DOI: 10.48550/arxiv.2607.15340

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