Comet Finlay
A comet that gave birth to a new southern meteor shower, the Arids, first seen in 2021.
Key facts
- Designation
- 15P/Finlay
- Type
- Jupiter-family comet
- Orbital period
- about 6.5 years
- Closest to the Sun
- about 1.0 AU (about 150 million km)
- Farthest from the Sun
- about 6 AU
- Tilt of orbit
- about 7°
- Nucleus
- about 2 km across
- Discovered
- by William Henry Finlay at the Cape of Good Hope on 26 September 1886
- Returns
- at perihelion in 2021; next in 2027
Orbit
Finlay goes round the Sun every six and a half years, close to the plane of the planets, from about Earth's distance out beyond Jupiter. Its dust meets Earth slowly, at about 11 km/s, almost the lowest speed possible.
Size and nature
The nucleus is small, probably about 2 km across. Late in 2014 and again in January 2015 the comet had two sudden outbursts, brightening enough to be seen in binoculars as fresh ice and dust burst out.
History
William Henry Finlay, First Assistant at the Royal Observatory at the Cape of Good Hope, found the comet in 1886. It has been seen at most returns since. For a long time no meteor shower was linked with it, because its orbit did not quite reach Earth's.
Meteor showers
Calculations showed that dust thrown out at certain past returns had been nudged into Earth's path. On 29 and 30 September 2021 observers in the southern hemisphere saw a new shower from the constellation Ara, the Altar. Called the Arids, it produced slow meteors and some bright ones. It was a rare chance to watch a shower appear for the first time, and it showed that forecasts of where comet dust will be are now good enough to predict a new shower before anyone has seen it.
Its meteor showers
- The Arids peak around late September to early October, in some years; about usually none; weak outbursts in 2021 an hour at best; about 15 km/s
Key dates
| Date | What happened |
|---|---|
| 26 September 1886 | William Henry Finlay discovered Comet Finlay at the Cape of Good Hope. |
| 29 September 2021 | The Arids, a new shower from Comet Finlay, were seen from the southern hemisphere. |
Did you know?
Arid meteors enter the atmosphere at only about 11 km/s.
The shower is named after Ara, the Altar, a southern constellation.
Finlay's outbursts of 2014 and 2015 came months before it reached the Sun.