Did an Ancient Cosmic Visitor Just Explode Near the Sun?

An object arrived from beyond our solar system this summer. Scientists are now debating whether it blew itself apart near the Sun — or whether the numbers point to something unusual about what this object really is.

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A Visitor From Another Star

Back on July 1, 2025, a telescope in Chile spotted something unusual streaking through space. The discovery got reported as comet 3I/ATLAS — only the third known interstellar object ever observed passing through our solar system. Astronomers went digging through archives and found the object had actually been photographed earlier. Earlier observations stretched back to June 14, 2025.

An amateur astronomer named Sam Deen found even older observations from early June 2025. He figured out why nobody spotted it sooner — 3I/ATLAS was passing in front of a region of space packed with stars, where a comet would be incredibly hard to pick out.

The speeds involved are absurd. When astronomers first identified 3I/ATLAS, the interstellar comet was traveling about 137,000 miles per hour. That’s fast enough to fly from New York to Los Angeles in less than two minutes.

When 3I/ATLAS entered our neighborhood, it was moving at 58 kilometers per second relative to the Sun. That’s significantly faster than the previous two interstellar visitors we’ve discovered. The first one, 1I/’Oumuamua, was traveling at 26 kilometers per second when astronomers spotted it in 2017. The second, 2I/Borisov, moved at 32 kilometers per second when found in 2019.

The path of 3I/ATLAS is almost a straight line through our solar system. Objects that orbit within our solar system follow curved paths. Anything on a nearly straight path is just passing through — it came from somewhere else and it’s heading back out.

Astronomers suspect that 3I/ATLAS could be the oldest comet ever observed. The object’s origins trace to somewhere in the galaxy. When 3I/ATLAS arrived, it was moving in unusual directions compared to most stars and objects near us. This means the comet follows a tilted path around the Milky Way rather than traveling in the same plane as most objects.

Close Encounter With the Sun

3I/ATLAS reached its closest point to the Sun around October 30, 2025, at a distance of about 130 million miles — just inside the orbit of Mars. During this close pass, spacecraft orbiting Mars got a unique opportunity to observe the visitor up close.

Two European spacecraft that normally study Mars both turned their cameras toward 3I/ATLAS between October 1 and 7, 2025. During the comet’s closest approach to Mars on October 3, it was about 30 million kilometers away from those spacecraft.

Each spacecraft used its camera to watch the comet pass. Both cameras are designed to photograph the surface of Mars from much closer, so scientists weren’t sure what to expect from observations of a dim target so far away. In the images, comet 3I/ATLAS appeared as a slightly fuzzy white dot moving near the center of the frame.

The faint comet was observable from October 18 to 24 with a weather satellite that can see objects down to a certain brightness level. During the same period, other Sun-watching satellites also tracked its progress.

Scientists detected something unexpected during the close solar passage. Astronomers in South Africa used a radio telescope on October 24 to observe the visitor. Two previous attempts in September had come up empty, but the third time worked. The team detected signals from hydroxyl radicals — molecules that get produced when water molecules are broken down by sunlight.

What the Telescopes Revealed

Earlier observations had provided clues about what the object is made of. Data from the Webb telescope showed that when 3I/ATLAS was farther from the Sun, 87% of the gas around it was carbon dioxide. Researchers also found increasing levels of nickel vapor as it got closer to the Sun.

The water detection changed how astronomers understood the object. NASA’s Swift Observatory detected hydroxyl gas, a chemical fingerprint of water. This discovery represented a major breakthrough.

Previous observations by the James Webb Space Telescope had hinted that 3I/ATLAS is mostly made of carbon dioxide ice, with only a trace of water accounting for four percent of its mass. Some scientists had started wondering if this visitor from another star system was fundamentally different from comets in our own solar system.

Finding hydroxyl radicals — and by extension, water — meant scientists could study the ancient visitor with familiar tools. When astronomers look at comets from our own solar system, they analyze water to measure how active that comet is. Finding the same signal in an interstellar object meant researchers could use the same methods.

Dennis Bodewits, a physics professor at Auburn University, explained the significance. When astronomers detect water from an interstellar comet, they’re essentially reading a message from another planetary system. It shows that the ingredients for life’s chemistry aren’t unique to our own corner of space.

Zexi Xing, a researcher who led the study about the water detection, pointed out how each interstellar comet has been a surprise. ‘Oumuamua appeared dry. Borisov was rich in carbon monoxide. Now 3I/ATLAS was giving up water at a distance where researchers didn’t expect it. Each one changes what scientists thought they knew about how planets and comets form around stars.

The Size Problem

From Hubble Space Telescope observations in August 2025, astronomers determined that the comet’s core is no bigger than 5.6 kilometers across. That size limit became crucial to understanding what happened next.

On November 9, 2025, new images revealed something dramatic. Two British astronomers captured detailed images showing multiple jets shooting outward from the comet. These jets extended about one million kilometers toward the Sun and three million kilometers in the opposite direction.

The visual was striking. One “smoky” tail extended upward and to the right, spanning roughly the apparent size of the Full Moon in our sky. The other tail, made of dust particles, extended downward and to the left — toward the Sun.

Harvard astronomer Avi Loeb started doing calculations based on what these jets meant for a natural comet. For jets made of ice turning into vapor, the speed would be expected at about 0.4 kilometers per second. At that speed, the jets must have been streaming outward for somewhere between one and three months to reach the distances seen in the images.

The jets heading toward the Sun were stopped by the solar wind at a distance of one million kilometers. That gave Loeb enough information to calculate how much material was flowing out. The math showed a mass loss of 5 billion tons per month.

His earlier calculations suggested the total mass of 3I/ATLAS is at least 33 billion tons. If the object was losing 5 billion tons per month, that meant 3I/ATLAS may have shed approximately 16% of its mass during its close pass by the Sun.

The math stops making sense here.

To supply 5 billion tons of carbon dioxide over a month, 3I/ATLAS must have received enough energy from sunlight to turn all that ice into gas. Running the numbers, the surface area of 3I/ATLAS would need to be larger than 1,600 square kilometers. That’s the area of a sphere with a diameter of 23 kilometers.

Hubble imaging data showed the maximum diameter is 5.6 kilometers. The required diameter is more than four times larger than what the Hubble Space Telescope actually observed. If the ice was mostly water instead of carbon dioxide, the required diameter jumps to 51 kilometers.

The required surface area to provide the mass loss is at least 16 times larger than the upper limit from Hubble observations.

As Loeb wrote in his November 10 analysis, “Houston, we have a problem with the natural comet hypothesis.”

The Dramatic Mass Loss

When the Webb telescope collected data on August 6, 2025, 3I/ATLAS was losing only 150 kilograms per second. The mass loss at its closest point to the Sun calculated from the November images was about 2 million kilograms per second — more than 13,000 times faster.

That’s not a gradual increase. It’s an explosion of activity.

Loeb’s analysis suggested a straightforward explanation if 3I/ATLAS is a natural comet. To increase the surface area by a minimum factor of 16, the object would need to break into at least 16 equal pieces, and likely many more. The implication: the latest images suggest 3I/ATLAS exploded at its closest pass to the Sun, torn apart by heating.

Breaking into fragments would have increased the surface area of the material. More pieces means more total surface area exposed to sunlight. The math suggested that 3I/ATLAS broke apart and observers were witnessing the resulting fireworks.

If that’s what happened, the pull of the Sun should separate those fragments over the coming weeks. This would create an appearance similar to comet Shoemaker-Levy 9 in 1994, which famously broke apart before colliding with Jupiter. Loeb had discussed this possible outcome a month before the close pass.

Did It Actually Explode?

On November 10, 2025, multiple news outlets ran with headlines suggesting 3I/ATLAS had exploded or broken apart. The story spread quickly — a mysterious interstellar visitor possibly disintegrating after its brush with the Sun.

Then, on November 11, 2025, Qicheng Zhang at the Lowell Observatory in Arizona looked at the latest images and came to a very different conclusion. Zhang, who has been studying the comet, told Live Science that all the images he’d seen showed a fairly ordinary, healthy-looking comet. There was no sign at all that the core broke apart.

The observations showed 3I/ATLAS displaying two distinct tails. Michael Jäger observed the tail on November 8, 2025. Gianluca Masi from the Virtual Telescope Project captured images from Italy on November 11 that showed the comet looking normal. Not exploded. Not fragmented.

So what’s going on? The mathematical problem Loeb identified is real — the surface area required by the mass loss calculations doesn’t match the size observations from Hubble. The dramatic increase in activity at the close pass actually happened. But the core appears intact.

This creates three possibilities. First, maybe the calculations about mass loss are wrong somehow, or there’s a mechanism for the observed jets that doesn’t require the massive surface area. Second, maybe the object did fragment but the pieces are still traveling together in a tight cluster that looks like a single object. Third, maybe 3I/ATLAS isn’t a natural comet at all.

The Statistical Anomalies

The size of 3I/ATLAS highlights another puzzle that has nothing to do with whether it broke apart.

The inferred mass of 3I/ATLAS is over a million times more than the inferred mass of 1I/’Oumuamua. Why would astronomers find such a giant object before witnessing a million objects of ‘Oumuamua’s size?

Loeb calculated that there simply isn’t enough rocky material in interstellar space to accommodate the delivery of such a large icy object to the inner solar system over a survey period of just a decade. An object with a diameter above 10 kilometers should arrive in our vicinity once per ten thousand years or longer.

The probability of finding 3I/ATLAS when we did is less than 0.1% if all rocky materials are packaged in large bodies of this size. That drops to less than 0.0005% if you account for how planetary systems typically form.

The path adds another layer of improbability. The plane of 3I/ATLAS’s orbit around the Sun lies within 5 degrees of Earth’s orbital plane. Out of all the random orientations an interstellar object could have, the likelihood of that alignment is 0.2%.

Combine the size probability with the trajectory probability, and you get odds of about one in a hundred million for 3I/ATLAS to arrive with these characteristics if it has a familiar origin.

The Alternative Hypothesis

Loeb has pointed out that technological thrusters would require much smaller mass loss to produce the observed jets around 3I/ATLAS. Chemical rockets propel themselves with an exhaust speed of 3 to 5 kilometers per second — ten times larger than the maximum speed of gas sublimated by sunlight from natural comet surfaces. Ion thrusters reach even higher speeds of 10 to 50 kilometers per second. More advanced propulsion systems might employ yet higher speeds, reducing the required mass loss by several orders of magnitude.

This isn’t the first time Loeb has suggested we might be looking at artificial objects from other civilizations. In 2018, he and a colleague published a paper suggesting that ‘Oumuamua might be an artificial thin solar sail accelerated by solar radiation pressure.

That first interstellar visitor displayed unusual characteristics. After slingshotting around the Sun, ‘Oumuamua sped up and deviated from its expected trajectory, apparently propelled by a mysterious force. Comets do that too, but they show visible evidence of gas and dust streaming off the surface. ‘Oumuamua showed no such evidence. The object also tumbled in a strange way and was unusually bright.

Before encountering our Sun, ‘Oumuamua was essentially at rest relative to nearby stars — statistically very rare. Rather than thinking of it as a vessel hurtling through space, from the object’s perspective, our solar system slammed into it.

The scientific community has largely reached consensus that ‘Oumuamua had properties entirely consistent with a naturally occurring object. By 2021, most astronomers agreed it was perhaps made of nitrogen ice, or a comet-like body altered by warming as it traveled through the solar system. Several researchers have criticized Loeb’s hypotheses about alien spacecraft , with some refusing to engage with his work.

For 3I/ATLAS, most researchers remain confident it’s a natural object. Richard Moissl at the European Space Agency told Newsweek that there have been no signs pointing to non-natural origins in the available observations. The analysis from many astronomers around the globe shows that 3I/ATLAS is consistent with being an icy object that formed around another star and was later scattered out of its home planetary system.

Recent observations by the Very Large Telescope detected molecules familiar from comets that originated within our Solar System. While the chemical mix in 3I/ATLAS is slightly different, those variations likely reflect the differences in its home star system compared to ours, not evidence of alien engineering.

Beyond its appearance, 3I/ATLAS also behaves like a comet, with its trajectory showing no sign of deliberate course changes or propulsive maneuvers. The object is simply coasting through space, reflecting sunlight as it passes by, exactly as a natural object would.

What Happens Next

After 3I/ATLAS passed its closest point to the Sun, it became visible in the sky again just before sunrise in November 2025. The comet is now heading back into darker skies. It’s expected to shine around magnitude 11 to 12 — too faint for the naked eye, only possibly visible in good binoculars under ideal dark-sky conditions, though small telescopes will show it more reliably.

During December 2025, the comet will move through the constellations Virgo and Leo. Its brightness is expected to drop and keep fading. As the year ends, the comet will drift away, eventually leaving the Solar System behind forever.

On December 19, 2025, 3I/ATLAS will get closest to Earth at a distance of about 269 million kilometers or 167 million miles. This will give ground-based telescopes as well as the Hubble and Webb space telescopes opportunities to examine the comet in detail and determine whether it’s intact or fragmented. Those observations should settle the question.

The European Space Agency’s Jupiter mission attempted observations in November 2025 using several instruments. Scientists don’t expect to receive data from those observations until February 2026.

The James Webb Space Telescope is scheduled to make its next observations of 3I/ATLAS in December 2025. Hubble will perform measurements to determine the composition of the gas and will monitor the comet on its way out of the Solar System.

After Earth, 3I/ATLAS will pass about 54 million kilometers from Jupiter on March 16, 2026. How much of its core will be left by that time remains to be seen.

Upcoming observations will determine the velocity, mass, and composition of the jets. These measurements will help answer whether the dramatic mass loss can be explained by natural processes or requires reconsidering the object’s nature.

The Bigger Picture

The European Space Agency is preparing the Comet Interceptor mission, due to launch in 2029 into a parking orbit where it will wait for a suitable target. The spacecraft will aim for a pristine comet from the distant Oort Cloud that surrounds our Solar System or, unlikely but appealing, an interstellar object like 3I/ATLAS.

When Comet Interceptor was selected in 2019, scientists only knew of one interstellar object — 1I/’Oumuamua, discovered in 2017. Since then, two more such objects have been discovered, showing large diversity in their appearance. Visiting one could provide a breakthrough in understanding their nature.

The mission will be the first to visit a comet coming directly from the outer reaches of the Sun’s realm, carrying material untouched since the dawn of the Solar System. It’s unlikely that astronomers will discover an interstellar object that’s reachable for Comet Interceptor, given their rarity. Still, as a first demonstration of a rapid response mission that waits in space for its target, it will serve as a pathfinder for possible future missions to intercept these mysterious visitors.

Interstellar comets offer scientists tangible connections to the broader galaxy. They provide chemical and physical details from distant star systems and reveal information about where those objects formed, and when. Each interstellar visitor carries clues about planetary formation in environments completely different from our own solar system.

For now, 3I/ATLAS continues its journey through our solar system. Carrying material from a distant planetary system, now observed and debated by astronomers trying to understand what it is and where it came from.

The coming weeks will reveal more. Whether the object maintained its integrity or fragmented under solar heating, whether the dramatic mass loss can be explained by natural processes or requires alternative explanations, whether the statistical anomalies are just unlikely coincidences or hint at something more unusual.

3I/ATLAS entered our solar system this summer as the third known interstellar object ever observed. It may leave having taught us something fundamental about comets from other star systems. Or it may leave us with more questions than answers about what we actually witnessed passing through our cosmic neighborhood.

References

NOTE: Some of this content may have been created with assistance from AI tools, but it has been reviewed, edited, narrated, produced, and approved by Darren Marlar, creator and host of Weird Darkness — who, despite popular conspiracy theories, is NOT an AI voice.