Reference image
Object guide
Halley's Comet is the best-known periodic comet, visible from Earth approximately every 75 years. Historical records of its appearances go back millennia; it was the first comet proven to be periodic. Halley's Comet is approximately 22 km across.
How to observe Halley's Comet
Halley's Comet changes in brightness and position around perihelion. Confirm a current ephemeris before observing because catalogue orbital values alone are not a live forecast.
Scientific context
Useful scale comparisons are 0.002 Earth diameters, 0 g surface gravity, 75.277 Earth years per orbit. These values are rounded from the catalogue measurements shown on this page.
- Radius
- 11 km
- Diameter
- 22 km
- Mass
- 220,000,000,000,000 kg
- Mean density
- 0.039 g/cm³
- Surface gravity
- 0.0001 m/s² (0 g)
- Orbital period
- 27,495 days (75.277 years)
0.002 Earth diameters0 g surface gravity75.277 Earth years per orbit
Source: NASA/JPL Small-Body Database (checked 2026-08-09). Values are rounded catalogue measurements.
Interactive orbit model
Aug 13, 2026, 22:251×
Calculated positions / separate exploration scales