Halley Time Machine
Halley's Comet is out past Neptune's orbit right now. It turned around at aphelion in December 2023 and is falling back toward the Sun for 2061. But its crumbs never left: Earth crosses the comet's old dust trail twice a year, in May and in October.
Orbit simulator
"Squashed" plots the square root of distance so Earth and Neptune both fit. Planets move on simple circular orbits; Halley's position is solved from Kepler's equation between its historical perihelion dates. Halley orbits backwards (retrograde) compared to the planets. Pink dots mark where Earth is on the Orionid and Eta Aquariid peak dates — close to where the comet's path crosses ours.
~75 years
Average time between returns. It varies between about 74 and 79 years as the planets tug on the comet.
0.59 → 35 au
Closest and farthest from the Sun: inside Venus's orbit at perihelion, beyond Neptune at aphelion.
15 × 8 km
The rough size of the nucleus, a dusty "dirty snowball" photographed by the Giotto probe in 1986.
Two showers
Halley's dust gives us the Eta Aquariids every May and the Orionids every October.
Halley through history
Each Orionid you catch in Night Watch is tagged with a pass of the comet it might have left on. Collect them all.
Years are perihelion years. The three ancient passes (1266, 1198 and 911 BC) come from orbital models of the 2006 Orionid outburst, not from historical records.