The Alpha Monocerotids meteor shower
Key facts
- Peak
- around 21–22 November
- Active
- about 15–25 November
- Rate at peak (ZHR)
- usually under 5; short outbursts of about 400 in 1995 and about 100 in 2019
- Speed
- 65 km/s
- Radiant
- Canis Minor and Monoceros (near Procyon)
- Parent body
- An unidentified long-period comet
Dates shift slightly from year to year. This year's peak is in the events calendar, and the meteor-shower planner shows how high the radiant climbs from where you live, night by night.
The Alpha Monocerotids are a shower that does almost nothing for years on end and then, for less than an hour, can fill the sky with fast meteors. They are one of the best examples of a short-lived outburst from a narrow dust trail.
Outbursts. Short bursts of activity were seen in 1925, 1935 and 1985. On 22 November 1995 observers in Spain and elsewhere in Europe saw rates of up to about 400 meteors an hour for around 30 to 40 minutes. Because the outbursts in 1925, 1935, 1985 and 1995 were roughly ten years apart, some writers spoke of a ten-year cycle, but the real cause is more subtle.
Why so brief? The parent is a long-period comet that has not been identified. Its dust forms a very narrow trail, released at one passage many centuries ago, which Earth crosses only in some years and only for a short time. The Finnish researcher Esko Lyytinen and Peter Jenniskens calculated where the trail would lie and predicted another outburst for 22 November 2019. It arrived within minutes of the predicted time, at about 04:50 to 05:00 Universal Time. Rates were about 100 an hour, lower than hoped, and the burst lasted only about 15 minutes. Most observers counted 10 to 20 meteors.
The radiant. The radiant is just south of Procyon in Canis Minor, close to the border with Monoceros, the faint Unicorn. Despite the name, it is not on Alpha Monocerotis. It rises in the east in the late evening and is high in the south before dawn.
What to expect. In most years, a meteor or two an hour at best. In an outburst year, fast, often bright meteors at about 65 kilometres per second, but only for minutes.
Viewing. The radiant is close to the celestial equator, so both hemispheres can see it. Whether an outburst is visible depends entirely on where it is dark at the predicted time. From the UK the radiant is well placed after midnight.
Viewing tips
- Check forecasts: any outburst lasts less than an hour.
- Be outside at least 30 minutes before the predicted time.
- Find Procyon, the bright star east of Orion, and look just south of it.
- Run a camera continuously through the predicted window.
- Expect fast meteors and keep counting even if the start is slow.