Howardites
Annual meteor shower

The Monocerotids meteor shower

Key facts

Peak
around 9 December
Active
about 1–19 December
Rate at peak (ZHR)
about 3
Speed
41 km/s
Radiant
Monoceros (east of Betelgeuse, near the border with Gemini)
Parent body
Comet C/1917 F1 (Mellish)

Dates shift slightly from year to year. This year's peak is in the events calendar.

The Monocerotids, or December Monocerotids, are a minor shower that peaks a few days before the Geminids and from a nearby part of the sky.

The parent comet. The stream comes from comet C/1917 F1, discovered in March 1917 by John Mellish, an American amateur astronomer and telescope maker. The comet takes several centuries to go round the Sun. Measured meteor orbits match the comet's well, and the link has been accepted for decades. Some researchers think the same comet may also feed other weak showers, including the April Rho Cygnids and a daytime shower in late summer.

The radiant. The meteors appear to come from Monoceros, the Unicorn, a faint constellation between Orion's Betelgeuse and Procyon. The radiant lies close to the border with Gemini. It rises in the evening and is highest around 1 to 2 am.

What to expect. About three meteors an hour, peaking around 9 December. The meteors are of medium speed, a little faster than the Geminids. Because both radiants are in the same general area, a meteor from that direction in early December is much more likely to be a Geminid. The Monocerotids are best separated from them with careful plotting or camera records.

Viewing from the UK. Good, because Monoceros is high in the south around 1 to 2 am in December. Nights are at their longest, though often cloudy.

Viewing worldwide. The radiant is just north of the celestial equator, so the shower can be seen from almost anywhere.

For most watchers, the Monocerotids are a bonus during Geminid sessions in the week before the main peak.

Viewing tips

  1. Watch around 1 to 2 am, when Monoceros is highest in the south.
  2. Find the faint area between Betelgeuse and Procyon.
  3. Expect slightly faster meteors than Geminids from a similar direction.
  4. Plot meteors carefully, or use a camera, to separate the two showers.
  5. Combine your watch with early Geminids around 9 December.

Read about the parent: Comet Mellish, and the other comets behind meteor showers.