Detection method

Excess Hyperbolic Velocity

The primary signature of an interstellar object: its speed relative to the Sun exceeds the local escape velocity by enough that the orbit is strongly hyperbolic (eccentricity well above 1). A large hyperbolic excess velocity (v∞) cannot be produced by planetary perturbations, so it points to an origin outside the Solar System. A small excess, by contrast, can come from a planetary slingshot and does not by itself prove an interstellar origin.

In brief

Measuring that an object's velocity exceeds Solar escape speed by a margin too large to be explained within the Solar System.

Objects identified this way

CNEOS 2014-01-08Debated origin
1I/ʻOumuamuaConfirmed interstellar
2I/BorisovConfirmed interstellar
3I/ATLASConfirmed interstellar

Sources

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

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.
NASA ADSNASA Astrophysics Data System
Bibliographic index of peer-reviewed astronomy and astrophysics literature.

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