Prepare to be amazed! We're about to dive into a story that will leave you in awe of the wonders of the universe and the power of human curiosity. Meet Larry Denneau, an astronomer with a unique skill set, who played a pivotal role in a discovery that shook the astronomical world.
On a seemingly ordinary July evening in 2025, Denneau, a senior software engineer and astronomer, was going about his routine at the University of Hawaii's Institute for Astronomy. Little did he know, this night would be anything but ordinary.
Denneau is part of the ATLAS team, an innovative network of telescopes designed to scan the night sky for potential threats to our planet - namely, near-Earth asteroids. The system employs a clever technique, capturing multiple images of the same patch of sky and creating a 'tracklet' to identify any movement. It's like a cosmic detective, searching for clues amidst the stars.
But here's where it gets controversial... On that fateful night, Denneau encountered something that didn't quite fit the typical asteroid profile. It was a moving point of light, but its trajectory suggested something far more intriguing. And this is the part most people miss: sometimes, the most extraordinary discoveries are made by those who dare to question the ordinary.
When Denneau reviewed the data, he saw a 'garden variety' Near Earth Object, as he put it. But his software, the very one he had designed, urged him to submit it for further review. And so he did, unknowingly setting in motion a chain of events that would lead to a groundbreaking revelation.
As the news of a new interstellar object spread, Denneau was nowhere to be found in the virtual realm. He was up in the mountains of Mauna Loa, tending to a telescope, effectively disconnected from the excitement building around this mysterious visitor.
But when he returned that night, reality hit him like a comet striking Earth. His inbox was flooded with messages, all centered around this enigmatic object. And as the data poured in from different telescopes, confirming its orbit, Denneau realized the magnitude of his discovery.
The object was classified as 3I/ATLAS, only the third interstellar visitor ever observed passing through our solar system. Unlike typical asteroids or comets, these interstellar objects are not bound to our sun; they are wanderers from other star systems, briefly visible as they traverse our cosmic neighborhood.
To find these elusive objects, software like ATLAS' looks for any moving points of light against a backdrop of stars. It's a delicate dance of technology and human expertise, where the final call rests with a person - in this case, Larry Denneau himself.
"I'm literally the person who clicked the button and submitted the discovery observations for this object," Denneau said with a sense of awe and responsibility.
As the models and follow-up observations came in, it became increasingly clear that 3I/ATLAS was not just another asteroid. Its orbit didn't conform to the familiar paths of objects bound to our sun. It was moving too fast, on a trajectory that suggested an origin beyond our solar system.
"All of the orbit fits turned out to be really poor. They didn't look like the solar system - they had this funny trajectory that said it's going really fast. It's not bound to the sun," Denneau explained.
And with that, the truth became undeniable: 3I/ATLAS was an interstellar comet, a visitor from another star system, a messenger from the cosmos.
But how did Denneau, an engineer-turned-astronomer, end up playing such a crucial role in this discovery?
Denneau doesn't fit the typical astronomer mold. His journey began with code, not stars. He started his career in engineering, mostly focused on computer programming. It was only later that he pursued a Ph.D. in astrophysics, combining his software skills with a passion for astronomy.
After moving to Hawaii, Denneau became deeply involved in building the software systems that underpin modern sky surveys. His expertise in both hardware and software gave him a unique perspective on astronomy, seeing it as a harmonious blend of both.
"We built some telescopes, but after the telescopes are built, it's really a software project," Denneau said. And it was this software project, one he helped develop, that captured the images of an interstellar comet.
Each night, the ATLAS telescopes capture thousands of images, covering an area equivalent to over 100 full moons at once. It's an immense undertaking, requiring custom software to process, compare, and filter the data, searching for any signs of movement, especially near-Earth asteroids.
"We have automated software that controls the telescopes, copies the data, and searches these images for things that are moving," Denneau explained. The volume of data is staggering, with four or five telescopes generating a good fraction of a terabyte every night. It's a challenge that keeps Denneau, the computer person, awake at night, ensuring the data is secure and backed up.
For Denneau, astronomy is as much a software project as it is a hardware endeavor. The system must efficiently ingest, clean, subtract, detect, match, and archive data, all while filtering out false positives that could lead other astronomers astray.
"We're really sensitive to not wanting to put false things on the confirmation page," Denneau said. "Because other telescopes will spend precious time chasing something that's not real."
ATLAS aims for near-perfect reliability, striving for a 99-point-something percent success rate before sending out an alert.
And Denneau's role in detecting moving objects doesn't end with 3I/ATLAS. Just months earlier, he was also on duty for the discovery of near-Earth asteroid YR4. Like 3I/ATLAS, YR4 first appeared as a faint moving point, and Denneau's expertise and software skills were crucial in confirming its existence and sending the data to the Minor Planets Center.
But why was 3I/ATLAS so difficult to detect in the first place?
Unlike YR4, finding earlier observations of 3I/ATLAS to model its origin was a challenging task. When it was first detected on July 1, 2025, the interstellar object happened to be moving through a crowded region of the sky, packed with stars from the Milky Way. This made detection much harder, as ATLAS requires four clean detections to officially flag a new object.
"When there's so many stars in the background, sometimes an asteroid goes right on top of a star. And so you only get three out. Because it was in the Milky Way, we had to kind of wait for it to get to a less dense part of the sky, for our pipeline to automatically admit it," Denneau explained.
But once 3I/ATLAS moved into a less cluttered region, the software did its job, and even uncovered earlier 'precovery' observations that helped confirm its unusual orbit.
Since its initial classification, 3I/ATLAS has captured the public imagination, making headlines and trending on social media. Interstellar visitors are rare, and each one offers a fleeting glimpse of material formed around another star, a cosmic connection that sparks our curiosity and wonder.
And in this case, that glimpse began not with a dramatic telescope view, but with software, data, and a person - Larry Denneau - who clicked a button at exactly the right time.
"Every day I still love coming to work and working on astronomy. It's just super fun," Denneau said with a smile.
So, what do you think? Are you amazed by the role software and human expertise play in these astronomical discoveries? Do you find the story of 3I/ATLAS and Larry Denneau inspiring? Let us know in the comments! We'd love to hear your thoughts on this extraordinary journey into the cosmos.
