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Loading contentVisitors from beyond the Solar System — and the Solar-System comets that merely look like them. This compact authority keeps confirmed interstellar objects, unconfirmed candidates, and hyperbolic Solar-System comets clearly apart, and explains how astronomers tell an object from another star from one of our own.
Unambiguously from beyond the Solar System — a strongly hyperbolic orbit and an IAU interstellar (“I”) designation.
The first confirmed interstellar object, detected in October 2017 on its way out of the Solar System. Its strongly hyperbolic orbit (eccentricity about 1.2) showed it was never bound to the Sun. It displayed no visible coma, is highly elongated, and showed a slight non-gravitational acceleration — features that drew wide attention, though the scientific consensus is that it is a natural body.
The second confirmed interstellar object and the first that was unmistakably a comet, discovered in August 2019 by amateur astronomer Gennadiy Borisov. Its eccentricity of about 3.4 made its interstellar origin certain. Unlike 1I/ʻOumuamua it showed an active dust coma and tail, letting astronomers study the chemistry of a comet formed around another star; it proved unusually rich in carbon monoxide.
The third confirmed interstellar object, discovered on 1 July 2025 by the ATLAS survey in Chile. Its orbit is the most strongly hyperbolic of the three found so far, with an eccentricity of roughly 6, and it showed cometary activity as it passed through the inner Solar System in late 2025. Some physical parameters remain preliminary, but its interstellar origin is established by the trajectory.
Proposed but not confirmed. These are never presented as catalogued interstellar objects — each carries an explicit uncertainty note.
A bright meteor (bolide) that entered Earth's atmosphere near Papua New Guinea on 8 January 2014, recorded in NASA CNEOS's fireball database. From the reported high velocity it was proposed in 2019 to have originated outside the Solar System, which would make it a candidate interstellar meteor. The claim is disputed: the underlying velocity data come from US Government sensors whose uncertainties are not public, and the interstellar interpretation is not accepted by the wider community. It is not a confirmed interstellar object.
Comets that formed here but were nudged onto hyperbolic or near-parabolic orbits — a small eccentricity above 1 from planetary perturbations, not an interstellar origin.
A long-period comet that a close encounter with Jupiter in 1980 flung onto a clearly hyperbolic orbit (eccentricity about 1.06). It is now leaving the Solar System, but — unlike a true interstellar object — it formed here; the hyperbolic orbit is the result of a planetary slingshot, not an origin around another star.
A near-parabolic long-period comet from the Oort cloud, famous for disintegrating completely near perihelion in July 2000 — one of the best-observed comet break-ups. Its orbit was close to the parabolic boundary (eccentricity near 1), the hallmark of a first-time visitor from the distant Solar System, not from interstellar space.
A long-period comet discovered by Andrea Boattini through the Mount Lemmon Survey, on a near-parabolic orbit with an eccentricity extremely close to 1. Like the other long-period comets here it is a distant Solar-System visitor, not an interstellar object: its original orbit is bound and it is not being ejected from the Solar System — the tiny excess over a parabola is an epoch-dependent, perturbed value.
A dynamically new, near-parabolic long-period comet discovered by Pan-STARRS in 2017 and notable for showing activity at a record distance — a coma was detected beyond Saturn's orbit, on the comet's first passage in from the Oort cloud. Its near-parabolic orbit marks it as a distant Solar-System visitor, not an interstellar object.
The eccentricity ladder, from bound orbits to interstellar trajectories — what makes an interstellar origin legible.
Measuring that an object's velocity exceeds Solar escape speed by a margin too large to be explained within the Solar System.
Fitting an orbit to astrometric positions and running it backward to show the object arrived unbound from outside the planetary region.
Comparing the light (spectra, colours) of a visitor with Solar-System bodies to characterise its composition.
The surveys that discover these objects and the bodies that catalogue them — the reused Pan-STARRS and the new ATLAS, Catalina, Minor Planet Center, and CNEOS entities.
Only three interstellar objects have been confirmed so far, but wide-field surveys are expected to find many more. The Legacy Survey of Space and Time at the Vera C. Rubin Observatory, in particular, should sharply increase the detection rate. This page states no predicted counts or dates — none are fabricated.
Each object, comet, detection method, trajectory class, and survey is a first-class knowledge-graph entity resolved through the Scientific Data Engine. Orbits and designations come from the IAU Minor Planet Center and the NASA/JPL Small-Body Database. Interstellar origin is asserted only for the confirmed objects; candidates carry explicit uncertainty notes and are never labelled confirmed. No “alien” or artificial-origin claims are made. Unknown values are left blank. See source quality.