Overview: A New View of 3I/ATLAS from an Exoplanet Mission
NASA’s Transiting Exoplanet Survey Satellite (TESS) isn’t limited to hunting planets around distant stars. In a surprising twist, the mission recently turned its gaze toward a visitor from beyond the Solar System: interstellar comet 3I/ATLAS. During a dedicated observation run from January 15 to January 22, 2024, TESS captured repeated views of the enigmatic traveler, offering scientists a rare chance to study its rotation and surface characteristics as it speeds away from us.
Why track an interstellar visitor with a planet-hunting telescope?
Exoplanet missions like TESS are optimized for detecting tiny dips in starlight caused by planets passing in front of their stars. Yet the same data streams can reveal a treasure trove of information about fast-moving objects within and beyond our solar system. By tracking 3I/ATLAS, researchers hope to infer the comet’s spin state, which in turn provides clues about its history, composition, and the forces acting on it as it plows through interstellar space.
What the observations revealed about 3I/ATLAS
During the seven-day observing window, TESS captured a sequence of light curves—graphs that show how the object’s brightness changes over time. Analysts looked for periodic patterns that correspond to rotational modulations caused by surface features turning in and out of view. Detecting such signals from a fleeting interstellar visitor is challenging, given its high velocity and varying brightness. However, the team reported hints of a measurable spin period, enabling researchers to constrain how fast 3I/ATLAS is rotating and how its surface reflects sunlight.
Potential clues about origin and structure
Spin rate and brightness variations can illuminate several aspects of an interstellar comet’s past. A rapid rotation might indicate a compact, cohesive nucleus, while slower spin or irregular brightness changes could point to a highly elongated shape or heterogeneous surface. By combining TESS data with ground-based observations and other space instruments, scientists aim to build a more complete model of 3I/ATLAS’s size, shape, and albedo (how much light it reflects).
How this fits into broader exoplanet and heliophysics research
The use of an exoplanet-hunting satellite to study an interstellar object underscores the versatility of space telescopes. While TESS’s primary mission remains identifying exoplanets around distant stars, its wide-field, high-cadence observations are well-suited to tracking fast-moving bodies in our celestial neighborhood. Insights gained from 3I/ATLAS might also refine techniques for monitoring future interstellar visitors, helping astronomers quickly characterize their spin, trajectory, and surface properties as they pass through the Solar System.
Future steps for studying 3I/ATLAS
NASA and collaborating institutions plan to coordinate follow-up observations across the electromagnetic spectrum. Spectroscopic data could reveal the comet’s composition, while high-resolution imaging from ground-based telescopes may provide more precise measurements of its nucleus and coma. As 3I/ATLAS continues its voyage, each new dataset will help piece together how such objects form, travel, and survive in interstellar space.
A milestone for interstellar exploration
Tracking 3I/ATLAS with a mission designed for exoplanets marks a milestone in the era of interstellar exploration. The ability to repurpose existing instruments to answer questions about objects from other star systems demonstrates the flexibility and ingenuity of the scientific community in pursuing answers about the universe we inhabit.
