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
The primary and reference sources this topic draws on.
- 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.