Credit: NASA, ESA and D. Jewitt (UCLA) Public Domain / NASA-ESA (credit required)

INTERSTELLAR OBJECT

2I/Borisov

The first confirmed interstellar comet — a normal-looking visitor from another star system.

First confirmed interstellar comet.
Discovered by amateur astronomer Gennadiy Borisov.
Composition normal for a cometary nucleus u2014 suggesting comets around other stars are much like our own.
Nucleus fragmented during and after March 2020 perihelion.

About 2I/Borisov

2I/Borisov is the first confirmed interstellar comet, discovered by amateur Ukrainian astronomer Gennadiy Borisov in August 2019 from his private observatory in Crimea. Unlike the rocky ‘Oumuamua, Borisov behaved like an ordinary comet — it displayed a visible coma and tail and its compositional inventory (CO, HCN, water) was roughly similar to Solar System comets, suggesting that comets around other stars are chemically not so different. The nucleus fragmented during and after its March 2020 perihelion.

Physical Properties

Mean radius1 km

Orbit

OrbitsGalactic

Semi-major axis-0.85 AU

Eccentricity3.357

Inclination44.05°

Gallery

Hand-picked mission imagery of 2I/Borisov sourced from NASA and partner archives. Click any photo for full resolution and source attribution.

Interstellar comet 2I/Borisov near perihelion, imaged by Hubble in December 2019. NASA, ESA and D. Jewitt (UCLA) · Public Domain / NASA-ESA (credit required)

Imagery on this page is provided by the original mission teams. Full attribution terms: Image Rights & Credits.

Sources & Further Reading

Numerical values (radius, mass, orbital elements, temperatures) are drawn from NASA NSSDC Planetary Fact Sheets, JPL Horizons, and the JPL Small-Body Database. Last refreshed: 2026-06-08 01:37:02.