Comet Machholz
A strange, sun-scorched comet at the centre of a family of comets and meteor showers.
Key facts
- Designation
- 96P/Machholz
- Type
- Jupiter-family comet that grazes close to the Sun
- Orbital period
- about 5.3 years
- Closest to the Sun
- 0.12 AU (about 17 million km), much closer than Mercury
- Farthest from the Sun
- about 5.9 AU
- Tilt of orbit
- about 58°
- Nucleus
- about 6 km across
- Discovered
- by the amateur astronomer Donald Machholz in California on 12 May 1986
- Returns
- at perihelion in 2023; next due in 2028
Orbit
Machholz passes closer to the Sun than any other short-period comet that is well known, coming within 17 million km, less than a third of Mercury's distance. At that range its surface is fiercely heated every five years. Its orbit is steeply tilted, and over thousands of years Jupiter slowly swings it round, which spreads its debris into several streams.
Size and nature
The nucleus is about 6 km across. In 2007 astronomers found that its gas is very poor in carbon and in cyanogen, a chemistry almost unknown among other comets. Explanations include repeated roasting by the Sun, birth in an unusually cold region, or even an origin around another star; none has been proved.
History
Donald Machholz, a dedicated American comet hunter, found it with binoculars from a mountain in California in May 1986. Since then the SOHO spacecraft, which watches the Sun, has filmed it at almost every return, when it can brighten briefly to about magnitude 2. Small fragments have been seen breaking away.
Meteor showers
Machholz is thought to be the largest surviving member of a group of comets and dust streams called the Machholz complex. It includes two families of tiny sungrazing comets found by SOHO, the Marsden and Kracht groups, as well as the Daytime Arietids, a strong shower in June detected by radar, and probably the Southern Delta Aquariids of late July. Some astronomers have suggested that the Quadrantids and their parent 2003 EH1 share the same ancestry, but that is less certain.
Missions
SOHO has observed the comet near the Sun on many returns.
Its meteor showers
- The Southern Delta Aquariids peak around 30–31 July; about 25 an hour at best; 41 km/s
- The Daytime Arietids peak around 7 June; about 30 (radio rates higher); few seen by eye an hour at best; 38 km/s
Space missions
- SOHO A solar observatory that has become the greatest comet discoverer in history.
Key dates
| Date | What happened |
|---|---|
| 12 May 1986 | Donald Machholz discovered the comet 96P/Machholz with binoculars. |
Did you know?
Donald Machholz spent thousands of hours searching for comets and found 11 or more.
The Daytime Arietids are one of the strongest showers of the year, but almost nobody sees them: they arrive in daylight.
The comet's chemistry is so unusual that it has been suggested, but not shown, to come from another star.