Interstellar comet reveals how alien worlds may differ from ours

Something strange and rare is passing through our solar system – a visitor from another star. It’s not sticking around. The object, known as 3I/ATLAS, is only the third interstellar comet ever detected.

An interstellar comet is a comet originating from outside of our solar system. Now, new images are helping scientists understand not only where 31/ATLAS came from, but also how other solar systems might differ from ours.

Interstellar comet hidden in plain sight

3I/ATLAS was officially discovered in early July, but it had already been in our skies, hiding in plain sight. It was simply too faint to notice.

Researchers dug through images from NASA’s Transiting Exoplanet Survey Satellite (TESS) and found that the object had actually appeared as early as May.

The experts looked at a part of the sky where the planets of our solar system orbit. That just happened to be the path 3I/ATLAS took on its journey through.

The team used a clever trick. They filtered out the glow from nearby stars, then stacked multiple images from different moments to sharpen the view. That’s how they spotted 3I/ATLAS with a surprising level of clarity.

Clues to alien chemistry

The early signs of activity were unexpected. Normally, comets only start to release gas and dust as they get close to the Sun. That’s what forms the glowing tail we see.

But 3I/ATLAS began showing activity much farther out – well before it came anywhere near the Sun’s heat.

This tells scientists that the interstellar object isn’t behaving like comets in our solar system. It’s likely made of different materials, such as carbon monoxide or carbon dioxide.

These substances can evaporate at lower temperatures than water. The discovery gives scientists new insight into how other solar systems might work.

Studying 3I/ATLAS before it disappears

Since it was found, astronomers across the globe have rushed to gather data on the object before it slips away for good. It will only be visible for a few more months before it’s out of reach – even for the most powerful telescopes on Earth.

The research was led by scientists at Michigan State University. They published their first paper about 3I/ATLAS just days after it was discovered.

“There are so few interstellar objects that we’ve detected in our solar system, and they each seem to be unique,” said Adina Feinstein, an assistant professor of physics and astronomy. “3I/ATLAS gives us an opportunity to study other solar systems up close and personal, without actually needing to visit them.”

Feinstein normally uses TESS data to search for exoplanets – planets that orbit stars far away. “As soon as I realized 3I/ATLAS should be in these TESS images, I downloaded them as quickly as I could,” she said.

What makes this interstellar comet different

The object’s full name – 3I/ATLAS – comes from two things. The “3I” means it’s the third known interstellar object. The “ATLAS” part refers to the telescope network that spotted it – NASA’s Asteroid Terrestrial-impact Last Alert System.

The more scientists studied the comet, the more unusual it seemed. It showed early signs of activity that point to a different chemical makeup than we’re used to seeing.

“That gives us an idea of what comets and asteroids could be made of in systems beyond our own Sun,” Feinstein said. “It’s always been assumed that other systems are different from ours, but now we have evidence of how different they might be.”

John Noonan, a postdoctoral fellow at Auburn University, said it’s crucial to find telescope images from before the comet was officially spotted.

“Capturing as many observations from this prediscovery period, where 3I/ATLAS may be in telescope images but wasn’t previously identified, is essential to our understanding of how these objects ‘turn on’ as they approach our Sun,” said Noonan.

“These interstellar objects have likely not been warmed significantly in millions – if not billions – of years, and any opportunity to see how they responded to that early heating is of interest.”

Searching for cosmic answers

The team plans to keep studying 3I/ATLAS as long as it’s visible. They’re using every tool they can – including NASA’s powerful James Webb Space Telescope – to figure out exactly what it’s made of and how it behaves.

In fact, astrophysicists across the world are working quickly to observe the comet and publish new findings.

The research also shows how missions like TESS – originally meant for studying stars and planets – can help answer bigger questions. Datasets from these missions are massive, and with the right approach, they can reveal surprises like this.

“Learning about other solar systems places humanity into context,” Feinstein said. “One of life’s greatest questions is ‘Are we alone in the universe?’ Each NASA mission brings us a little bit closer to answering this big, overarching question.”

The full study was published in the journal The Astrophysical Journal Letters.

Image Credit: NASA, ESA, David Jewitt (UCLA)

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