Interstellar object

3I/ATLAS

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.

Confirmed interstellarHyperbolic (e ≈ 6.1) — the most strongly hyperbolic yet found

Note

Discovered in mid-2025; some physical parameters remain preliminary. The interstellar origin rests on the strongly hyperbolic orbit, not on any claim of artificial origin.

Physical & orbital character

Origin:Unbound; the most strongly hyperbolic interstellar object found to date

Activity:An active comet — a coma was detected soon after discovery

Size:Nucleus uncertain — early estimates span a few hundred metres to a few kilometres

Composition:Cometary; detailed composition still being studied

How it was identified

Trajectory class:Interstellar Hyperbolic Trajectory

Detection methods:Excess Hyperbolic Velocity Incoming-Trajectory Analysis Spectroscopic Composition Analysis

Detected by survey:ATLAS

Catalogued by:Minor Planet Center NASA Jet Propulsion Laboratory

Knowledge connections

Trajectory classInterstellar Hyperbolic Trajectory
Associated withExcess Hyperbolic Velocity
Associated withIncoming-Trajectory Analysis
Associated withSpectroscopic Composition Analysis
Surveyed byATLAS
Catalogued inMinor Planet Center
Catalogued inNASA Jet Propulsion Laboratory

Sources

Facts on this topic will be cited from these primary and reference sources.

Minor Planet CenterIAU Minor Planet Center
Designations and orbits of asteroids, comets, and minor bodies.
NASA JPLJet Propulsion Laboratory / Solar System Dynamics
Orbital data, ephemerides, and small-body parameters for planets, asteroids, and comets.
NASANational Aeronautics and Space Administration
Mission data, planetary science, space telescopes, and public-domain imagery.
Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.

Quick facts

Confirmed interstellar

Designation: 3I/ATLAS
Discovered: 2025-07-01
Discovered by: ATLAS survey
Survey / facility: ATLAS, Río Hurtado, Chile
Eccentricity: 6.1 (hyperbolic)
Perihelion distance: 1.36 AU
Inclination: 175°
Excess velocity: ≈ 58 km/s (velocity relative to the Sun far from perihelion)
Perihelion date: 2025-10-29
Trajectory class: Interstellar Hyperbolic Trajectory

In the sky

Interstellar objects pass through the Solar System once and do not return; this encyclopedia computes no live positions or visibility. For what is genuinely observable tonight, use the Live Sky tools.

Quality & authority

38%

Unreviewed

Completeness: Complete
Source coverage: Complete
Citation coverage: None
Relationship coverage: Complete
Review coverage: None
Image coverage: None

Orbits and designations from the IAU Minor Planet Center and the NASA/JPL Small-Body Database. Unknown values are left blank. See source quality.

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3I/ATLAS

Confirmed interstellarHyperbolic (e ≈ 6.1) — the most strongly hyperbolic yet found

Sources

Facts on this topic will be cited from these primary and reference sources.

Minor Planet CenterIAU Minor Planet Center

Designations and orbits of asteroids, comets, and minor bodies.

NASA JPLJet Propulsion Laboratory / Solar System Dynamics

Orbital data, ephemerides, and small-body parameters for planets, asteroids, and comets.

NASANational Aeronautics and Space Administration

Mission data, planetary science, space telescopes, and public-domain imagery.

Most NASA-produced imagery is in the public domain; individual items are checked for usage terms before publication.

Quick facts

Confirmed interstellar

Designation

3I/ATLAS

Discovered

2025-07-01

Discovered by

ATLAS survey

Survey / facility

ATLAS, Río Hurtado, Chile

Eccentricity

6.1 (hyperbolic)

Perihelion distance

1.36 AU

Inclination

175°

Excess velocity

≈ 58 km/s (velocity relative to the Sun far from perihelion)

Perihelion date

2025-10-29

Trajectory class

Interstellar Hyperbolic Trajectory