A Stranger from Afar: Lowell Observatory Captures First Ground-Based Images of Interstellar Comet 3I/ATLAS

Lowell Observatory catches an interstellar visitor on camera — and why that matters now

Lowell Observatory has produced the first ground-based optical images of comet 3I/ATLAS, the third object known to have come from outside our solar system. The pictures arrived just as the tiny visitor was moving through the inner system, giving astronomers a chance to see whether this interstellar body behaves like a comet or something stranger.

The images are important not because they are dramatic on their own, but because ground telescopes can follow such objects for longer stretches than most space assets. That continuity lets researchers track how the comet releases gas and dust, changes brightness, and reacts to the Sun — all clues to where it came from and what it’s made of.

How the Lowell team imaged 3I/ATLAS: a 4.3-meter scope, a low horizon and careful processing

Lowell’s pictures were taken with the Lowell Discovery Telescope, a 4.3-meter instrument designed to do serious science rather than wide-field sky surveys. The team highlighted the telescope’s ability to observe objects low on the horizon — a useful trait when a fast-moving target is only briefly visible in the hours before dawn or after dusk.

To capture 3I/ATLAS, observers used short, repeated exposures to freeze the comet’s motion against the starry background. Those many frames were aligned and combined in software to boost faint details while avoiding streaks. The result is a clean optical image that shows the comet’s fuzzy coma — the cloud of dust and gas surrounding its nucleus — and hints of a tail.

Lowell’s researchers also ran basic image processing steps common in professional astronomy: subtracting the camera’s background glow, removing hot pixels and cosmic-ray hits, and calibrating brightness using known stars in the field. These steps don’t change what’s in the sky; they simply make faint structures easier to see and measure.

Third known interstellar object: how 3I/ATLAS compares with ‘Oumuamua and 2I/Borisov

There are only two firm precedents. The first, ‘Oumuamua, showed up in 2017 as a strange, hockey-puck–shaped object that brightened and dimmed in odd ways and did not show a visible coma. It looked more like a rocky fragment than a comet. The second, 2I/Borisov, arrived in 2019 and behaved like a normal comet: it had a bright coma, a tail and gas signatures in its spectrum.

3I/ATLAS so far seems closer to Borisov than to ‘Oumuamua. The Lowell images show a coma and a tail-like feature, which point to active release of dust and gas as the comet warms near the Sun. That makes 3I/ATLAS an excellent candidate for follow-up studies aimed at measuring its composition, rather than a weird inactive object that forces astronomers to invent exotic explanations.

All three objects share one defining trait: their paths are open to the Solar System, not bound by the Sun. They arrived from interstellar space, passed through our neighborhood on fast, one-time trajectories, and will head back out again — which is what makes catching them early and watching them closely so valuable.

Why these images matter — follow-ups and the questions they can answer

Even simple images tell astronomers how much dust the comet is shedding and how that dust is distributed. Combined with later observations, images help calibrate spectroscopy — the breakdown of light into its component colors — which can detect specific molecules, like cyanogen or water-related fragments. That, in turn, offers a peek at the chemistry of another star system.

Because 3I/ATLAS appears to be an active comet, broadband optical imaging is just the start. Astronomers will want spectra to see which gases are present, and infrared or radio observations to measure cold dust and certain molecules that don’t show up in visible light. Space telescopes, when available, can see past Earth’s atmosphere and pick out fainter signals.

Practically, this discovery also shows the value of having capable ground telescopes ready to react. Interstellar objects appear suddenly and vanish quickly. The Lowell images reduce uncertainty about 3I/ATLAS and make it easier to plan targeted campaigns across observatories worldwide while the comet is still bright enough to study.

Researchers respond, and a brief timeline of discovery to imaging

Lowell’s statement framed the images as an early look that will shape follow-up work. “These images give us our first ground-based optical view of 3I/ATLAS, and they guide what we’ll try to measure next,” a Lowell astronomer said in the release. The team emphasized the value of tracking the comet as it moves and evolves.

Timeline, in short: an automated survey first spotted 3I/ATLAS as a moving point of light. Astronomers quickly calculated its trajectory and recognized it as interstellar. The comet moved toward the inner Solar System and brightened as it warmed. Near that time, the Lowell Discovery Telescope captured the sequence of short exposures that were stacked into the images released to the public.

Lowell Observatory has a long history of reacting to transient sky events and contributing to follow-up networks. This set of images won’t answer every question about 3I/ATLAS, but it gives astronomers a firmer starting point for spectroscopy, longer monitoring and comparative work that could tell us whether our Solar System’s materials are typical or unusual in the galaxy.

Sources

• prnewswire.com