Toggle the switch to compare 2I/Borisov, an unbound interstellar visitor, side by side with Halley's Comet, a typical bound solar-system comet - drawn with a schematic open path vs a closed loop and a coma cloud sized by each object's real measured CO/H2O ratio.
Drag to orbit and scroll or pinch to zoom on the scene above. The two path curves show the open (unbound) vs closed (bound) shape difference only - they are not drawn to true AU distance.
For the first interstellar object's shape and tumbling motion instead of composition, see the 'Oumuamua 3D Explorer. For a bound solar-system comet's own orbit mechanics, see the Comet Orbit 3D Explorer.
2I/Borisov Interstellar Comet 3D Explorer
Toggle between 2I/Borisov and Halley's Comet in this browser explorer to see why an interstellar visitor's orbit shape and coma chemistry differ from a typical bound solar-system comet, using the real measured eccentricity and CO/H2O ratio for each.
2I/Borisov is only the 2nd confirmed interstellar object, discovered on 30 August 2019 by amateur astronomer Gennadiy Borisov in Crimea. Within about 2 weeks, astronomers confirmed its orbit was hyperbolic - with a refined eccentricity of about 3.36, well above the value of 1 that marks the boundary between a bound and an unbound path, meaning 2I/Borisov came from outside the solar system and is now leaving it forever. It reached perihelion, its closest approach to the Sun, at about 2.01 AU on 8 December 2019, moving at about 43.9 km/s at that point and slowing to about 32.3 km/s at infinity, its interstellar cruising speed. Hubble Space Telescope imaging found a small nucleus with an effective radius of roughly 0.2-0.5 km. Unlike the first known interstellar object, 1I/'Oumuamua, which showed no detectable outgassing, 2I/Borisov actively displayed a visible coma just like an ordinary solar-system comet - but its chemistry was unusual. Hubble spectroscopy (Bodewits et al. 2020, Nature Astronomy) measured a carbon monoxide to water production-rate ratio of about 35-155% for 2I/Borisov, compared with about 4% for a typical solar-system comet; an independent ALMA radio measurement (Cordiner et al. 2020, same journal) found its CO abundance roughly 9-26 times higher than typical inner-solar-system comets, pointing to a different protoplanetary-disk origin. For comparison, Halley's Comet - a well-studied, bound solar-system comet - has an orbital eccentricity of about 0.967, a perihelion distance of about 0.59 AU, and returns to the inner solar system on a period of about 76 years.
- Toggle switch (0-1) swaps the highlighted comet between 2I/Borisov and Halley's Comet, redrawing the facts panel with that object's real published figures
- Two schematic path curves show the shape difference between an unbound hyperbolic path and a closed elliptical loop - illustrative shape only, not to true AU distance scale
- Each comet's coma is a particle cloud drawn around a stylized nucleus, with density set by that object's real measured CO/H2O production ratio
- A comparison table ranks both objects' orbital eccentricity and CO/H2O ratio side by side, with the active object highlighted
- Drag to orbit, scroll or pinch to zoom
- Runs fully in the browser with the vendored three.js engine - no account, no upload
| Object | Orbit | Perihelion | CO/H2O ratio |
|---|---|---|---|
| 2I/Borisov | eccentricity about 3.36 - unbound, leaves forever | about 2.01 AU (8 Dec 2019) | about 35-155% (Hubble) |
| Halley's Comet | eccentricity about 0.967 - bound, ~76-year period | about 0.59 AU | about 4% (typical average) |
For the first interstellar object's shape and tumbling motion rather than its composition, open the 'Oumuamua 3D Explorer. For a bound solar-system comet's own orbit mechanics in detail, see the Comet Orbit 3D Explorer.
Everything renders on your device with WebGL. The 3D engine loads once (about 0.7 MB) and is cached.
This is an educational approximation - both nuclei are stylized scaled spheres, not scanned shapes; the coma is drawn as a radially-expanding particle cloud, not a directional tail shaped by solar wind and radiation pressure; and the two path curves show the open vs closed shape difference only, not true AU distances.
Frequently Asked Questions
What is 2I/Borisov?
2I/Borisov is only the 2nd confirmed interstellar object, discovered on 30 August 2019 by amateur astronomer Gennadiy Borisov in Crimea. Unlike the first, 1I/'Oumuamua, it actively outgassed a visible coma like an ordinary comet.
How do we know 2I/Borisov's orbit is unbound?
Within about 2 weeks of discovery, astronomers confirmed its orbit was hyperbolic, with a refined eccentricity of about 3.36 - well above 1, the boundary between a bound and an unbound path. It came from outside the solar system and is leaving forever.
How fast was 2I/Borisov moving?
About 43.9 km/s at perihelion (its closest approach to the Sun, about 2.01 AU, on 8 December 2019), slowing to about 32.3 km/s at infinity - its interstellar cruising speed.
What makes 2I/Borisov's coma unusual?
Hubble spectroscopy (Bodewits et al. 2020) measured a carbon monoxide to water production-rate ratio of about 35-155%, compared with about 4% for a typical solar-system comet. An independent ALMA measurement (Cordiner et al. 2020) found its CO abundance roughly 9-26 times higher than typical inner-solar-system comets.
How big is 2I/Borisov's nucleus?
Hubble Space Telescope imaging found a small nucleus with an effective radius of roughly 0.2-0.5 km.
How does 2I/Borisov compare to Halley's Comet?
Halley's Comet is bound to the Sun with an orbital eccentricity of about 0.967 and returns on a roughly 76-year period, with a typical CO/H2O ratio of about 4%. 2I/Borisov is unbound (eccentricity about 3.36) and will never return, with a far higher CO/H2O ratio.
Is the on-screen comet shape or coma to scale?
No. Both nuclei are stylized scaled spheres, not scanned shapes, and the coma is drawn as a radially-expanding particle cloud rather than a directional tail shaped by solar wind. The two path curves show the open vs closed orbit shape only, not true AU distances.
Where do these figures come from?
NASA/JPL Small-Body Database and Center for NEO Studies orbital elements for 2I/Borisov, Bodewits et al. 2020 and Cordiner et al. 2020 (both Nature Astronomy), Hubble Space Telescope nucleus-size reporting, and NASA's 1P/Halley science page.