Alpha Monocerotids
A normally weak shower that can produce brief, intense meteor storms.
The Alpha Monocerotids meteor shower occurs each year from November 15 to 25, peaking around November 21 or 22. Its meteors streak through the sky at 65 km/s, which is near the theoretical upper limit for meteor speed of roughly 73 km/s. The shower typically has a low Zenithal Hourly Rate (ZHR), but it sometimes produces brief, intense meteor storms lasting less than an hour. Such outbursts were recorded in 1925, 1935, 1985, and 1995, with the 1925 and 1935 storms each exceeding 1,000 ZHR.
Peter Jenniskens predicted the 1995 return based on the idea that planetary perturbations occasionally push the dust trail of a long-period comet into Earth’s path. Observing from southern Spain with a team from the Dutch Meteor Society, Jenniskens confirmed that the meteoroids followed a long-period comet orbit. The 1995 outburst allowed researchers to pinpoint the exact radiant and the solar longitude of the peak, and to confirm that these outbursts last less than an hour. The parent body, likely a long-period comet, remains unknown.
In 2019, Jenniskens and Esko Lyytinen forecast an outburst starting around 04:50 UTC on November 22 (11:50 p.m. EST November 21), lasting roughly 15 minutes and reaching 400 meteors per hour—similar to the 1995 rate. However, although the peak occurred at 05:00 UTC, the actual rate was much lower than predicted.
Quick Facts
- Parent
- Unknown
- Constellation
- Monoceros
- Ra
- 7 · 48 · 00
- Dec
- +1 · 00 · 00
- Month
- November 15 to November 25
- Peak
- November 21-22
- Velocity
- 65
- Zhr
- variable
Facts from the source article.
Lore & Background
The Alpha Monocerotids is known for occasional outbursts that last less than an hour. Such outbursts were observed in 1925, 1935, 1985, and 1995. The 1925 and 1935 storms both reached levels passing 1,000 ZHR. Peter Jenniskens predicted the 1995 return based on the hypothesis that these outbursts were caused by the dust trail of a long period comet occasionally wandering in Earth's path due to planetary perturbations. During observations in southern Spain, assisted by a team of observers of the Dutch Meteor Society, Jenniskens confirmed that the meteoroids were moving in a long-period comet orbit. The outburst of 1995 allowed researchers to determine the exact radiant of the swarm and the solar longitude of its peak as well as to confirm the brevity of Alpha Monocerotid outbursts as less than one hour. The parent body, probably a long-period comet, is unknown.
Reader's Guide
The Alpha Monocerotids is significant for its rare but dramatic outbursts, which provide a window into the dynamics of long-period comet dust trails. The 1995 outburst, predicted by Peter Jenniskens based on planetary perturbations, was a landmark event that allowed researchers to precisely determine the radiant and solar longitude of the swarm, and to confirm that these outbursts last less than an hour. The 2019 prediction by Jenniskens and Esko Lyytinen, though the actual rate was much lower than forecast, demonstrated ongoing efforts to model these brief storms. The shower's parent body remains unknown, but its meteoroids travel in a long-period comet orbit, linking it to the outer solar system. Its legacy lies in advancing the understanding of how dust trails from long-period comets can occasionally intersect Earth's path, producing short-lived but intense meteor activity.
Did You Know?
- The Alpha Monocerotids can produce outbursts that last less than an hour.
- Peter Jenniskens predicted the 1995 return based on planetary perturbations of a long-period comet's dust trail.
- The parent body of the Alpha Monocerotids is unknown, but is probably a long-period comet.
Frequently Asked Questions
What is the Alpha Monocerotids?
It is a minor annual meteor shower that shows up in mid-to-late November, with its best viewing window landing on the 21st or 22nd. Under normal conditions it is a very quiet shower, but it is famous for occasionally erupting into a short, spectacular storm that lasts barely an hour before vanishing.
How fast do Alpha Monocerotids meteors travel?
Each particle slams into the atmosphere at roughly 65 km/s, which puts it right up against the ~73 km/s ceiling that orbital mechanics allows for any meteor entering Earth's atmosphere. In practical terms, these are among the fastest streaks you will ever see in the night sky.
When are the famous Alpha Monocerotids storms?
Recorded outbursts occurred in 1925, 1935, 1985, and 1995. The 1925 and 1935 events were the most dramatic, each pushing past 1,000 meteors per hour at the zenith, while the 1985 and 1995 displays were also notably intense but shorter in duration.
Why do Alpha Monocerotids storms hit so unpredictably?
The debris stream is normally too sparse to produce anything beyond a handful of streaks per hour, but gravitational tugs from planets occasionally nudge the particle trail into a tighter, denser configuration that Earth plows through. Because those perturbations do not repeat on a simple yearly cycle, the big storms show up on an irregular, hard-to-forecast schedule.
How long does an Alpha Monocerotids storm actually last?
Even in its most spectacular outbursts the shower peaks for well under an hour before the dense clump of particles has passed. Observers in 1925 and 1935 had only a brief window to witness rates exceeding 1,000 ZHR, making each event a once-in-a-decade surprise rather than a steady multi-night display.
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