Interstellar object

2I/Borisov

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.

Confirmed interstellarHyperbolic (e ≈ 3.36) — unbound

Note

The first interstellar object with clear cometary activity, allowing spectroscopy of material from another planetary system.

Physical & orbital character

Origin:Unbound hyperbolic trajectory; no specific parent star has been identified

Activity:An active comet — dust coma and tail; a fragment separated in early 2020

Size:Nucleus below ~1 km across; likely a few hundred metres (uncertain)

Composition:Cometary ices and dust, with an unusually high carbon-monoxide abundance

How it was identified

Trajectory class:Interstellar Hyperbolic Trajectory

Detection methods:Excess Hyperbolic Velocity Spectroscopic Composition Analysis

Catalogued by:Minor Planet Center NASA Jet Propulsion Laboratory

Knowledge connections

Trajectory classInterstellar Hyperbolic Trajectory
Associated withExcess Hyperbolic Velocity
Associated withSpectroscopic Composition Analysis
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.
ESAEuropean Space Agency
European missions, observatories, and space science imagery.
ESOEuropean Southern Observatory
Southern-hemisphere observatory data and imagery (VLT, ALMA partner).

Quick facts

Confirmed interstellar

Designation: 2I/Borisov
Discovered: 2019-08-30
Discovered by: Gennadiy Borisov
Survey / facility: 0.65 m telescope, MARGO observatory, Crimea
Eccentricity: 3.36 (hyperbolic)
Perihelion distance: 2 AU
Inclination: 44.05°
Excess velocity: ≈ 32 km/s (velocity relative to the Sun far from perihelion)
Perihelion date: 2019-12-08
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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2I/Borisov

Confirmed interstellarHyperbolic (e ≈ 3.36) — unbound

Physical & orbital character

Origin:Unbound hyperbolic trajectory; no specific parent star has been identified

Activity:An active comet — dust coma and tail; a fragment separated in early 2020

Size:Nucleus below ~1 km across; likely a few hundred metres (uncertain)

Composition:Cometary ices and dust, with an unusually high carbon-monoxide abundance

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.

ESAEuropean Space Agency

European missions, observatories, and space science imagery.

ESOEuropean Southern Observatory

Southern-hemisphere observatory data and imagery (VLT, ALMA partner).

Quick facts

Confirmed interstellar

Designation

2I/Borisov

Discovered

2019-08-30

Discovered by

Gennadiy Borisov

Survey / facility

0.65 m telescope, MARGO observatory, Crimea

Eccentricity

3.36 (hyperbolic)

Perihelion distance

2 AU

Inclination

44.05°

Excess velocity

≈ 32 km/s (velocity relative to the Sun far from perihelion)

Perihelion date

2019-12-08

Trajectory class

Interstellar Hyperbolic Trajectory