Halley's Comet
What is Halley's Comet?
Comets· Nucleus 11 km. The first comet whose return was predicted. Recorded since 240 BC, it comes back in the summer of 2061 — replay its whole orbit in the simulator.
The orbit of Halley's Comet at this moment: https://nowsky.org/solar/orbit?fw=halley&sp=45 — replayed live, no login.
Past visits and the next return
Orbit and period
| Nucleus | ~11 km |
|---|---|
| Period | 76 yr |
| Next perihelion | July 2061 |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Frequently asked
- How long is the orbital period of Halley's Comet?
- 76 yr.
- When does Halley's Comet return?
- July 2061.
- In one line, what is Halley's Comet?
- Comets — The first comet whose return was predicted.
The Christmas of 1758, when the prediction came true
Halley predicted in 1705 that the comet would return at the end of 1758 and died in 1742. On the night of 25 December 1758 it was recovered by Johann Palitzsch, a farmer and amateur astronomer in Saxony, with his own telescope — weeks before the professional observatories. It was the first predicted return of a comet ever to happen, and the first popular proof that Newtonian mechanics could say in advance what the sky would do.
The timing was pinned down by Clairaut in France, who calculated that the gravity of Jupiter and Saturn would delay the comet and put perihelion in mid-April 1759; the actual date was 13 April, within a month. Nicole-Reine Lepaute, who shared the calculation, was left off the paper because she was a woman, and her contribution was forgotten for over two centuries before being acknowledged.
The comet in depth
Halley's Comet taught humanity that comets return. In 1705 Edmond Halley argued the comets of 1531, 1607 and 1682 were one object and predicted its 1758 return; sixteen years after his death it came back, and took his name.
Every apparition since 240 BC is on record — it hangs over the Battle of Hastings in the Bayeux Tapestry — and in 1986 ESA's Giotto flew close enough to photograph the nucleus: a peanut-shaped block of black ice, 15 × 8 km.
Next perihelion: July 2061. Replay its 76-year orbit in the orbit view and watch the extreme ellipse plunge from beyond Neptune to inside Venus's orbit.
The 1986 return was met by history's first comet armada: Europe's Giotto dove to 600 km and photographed the peanut-shaped nucleus — coal-black, reflecting just 4% of sunlight — joined by Soviet and Japanese probes. Halley's debris still returns twice a year as meteor showers: May's Eta Aquariids and October's Orionids are both its dust.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.