Comet Pons–Winnecke
A comet whose orbit Jupiter keeps reshaping, which explains the surprise outbursts of the June Bootids.
Key facts
- Designation
- 7P/Pons–Winnecke
- Type
- Jupiter-family comet
- Orbital period
- about 6.2 years
- Closest to the Sun
- about 1.2 AU at present; it has varied from 0.77 to 1.26 AU since 1819
- Farthest from the Sun
- about 5.6 AU, near Jupiter's orbit
- Tilt of orbit
- about 22°
- Nucleus
- about 5 km across
- Discovered
- by Jean-Louis Pons at Marseille on 12 June 1819; rediscovered by Friedrich Winnecke at Bonn on 9 March 1858
- Returns
- at perihelion in 2021 and 2027
Orbit
Pons–Winnecke goes round the Sun about every six years. Its far end lies near Jupiter's orbit, and close passes of the giant planet keep moving it. In 1819 its nearest point to the Sun was inside Earth's orbit; by 1989 it had moved out to well beyond. Calculations show it will move in again after another close pass of Jupiter in the 2030s. Its dust meets Earth slowly, at about 18 km/s.
Size and nature
The nucleus is about 5 km across. In 1927 the comet passed only about 6 million km from Earth, one of the closest comet passes on record at the time, and it has been well observed at many returns since.
History
Jean-Louis Pons, the most successful comet hunter of his age, found it in 1819. Friedrich Winnecke picked it up again in 1858 and showed it was periodic. In 1916 observers saw an unexpected burst of meteors from Boötes in late June, and the link to the comet was made. When the shower burst out again without warning in 1998, it reached around 100 to 200 meteors an hour.
Meteor showers
The June Bootids are usually so weak as to be almost invisible. In some years, though, Earth passes through old dust trails that Jupiter has nudged into our path, and the rate jumps. After the 1998 surprise, astronomers modelled these trails and correctly predicted a smaller outburst in 2004. The shower is a good example of how a planet's gravity, not just the comet, decides when a shower will be strong.
Its meteor showers
- The June Bootids peak around 23–27 June; about usually near zero; outbursts of 50–100 or more (1998) and 20–50 (2004) an hour at best; 18 km/s
Key dates
| Date | What happened |
|---|---|
| 12 June 1819 | Jean-Louis Pons discovered the comet now called Pons–Winnecke. |
| 9 March 1858 | Friedrich Winnecke rediscovered Comet Pons–Winnecke. |
Did you know?
Jean-Louis Pons began as a doorkeeper at the Marseille observatory and went on to find 37 comets.
The 1998 June Bootid outburst came from dust shed in the 1800s.
As the comet's orbit shifts, so does the shower: it may become stronger later this century.