Intense Meteor Outburst Expected from the Alpha Monocerotids

What's rarer than seeing a unicorn? How about a unicorn spitting meteors at the rate of 400 per hour? You'll have an opportunity to see it for yourself on Thursday night, November 21-22, when the obscure Alpha Monocerotid shower could produce upwards of 400 meteors per hour from a radiant near the star Procyon in Monoceros the unicorn. Even more amazing, the outburst is expected to last only a half-hour.

Peter Jenniskens, a senior research scientist with the SETI Institute and NASA's Ames Research Center, along with Esko Lyytinen of the Finnish Fireball Network, have been keeping tabs on the shower for years. During outbursts, such as those that occurred in 1925 and 1935, activity reached meteor-storm levels with a zenithal hourly rate (ZHR) of more than 1,000. Activity rose to near-storm levels again in 1985 and 1995 with ZHRs around 700 and 400. ZHR is an idealized number based on how many meteors a single observer would see if the radiant were overhead in a dark sky during shower maximum.

The source of the Alpha Monocerotids is unknown, but the stream's orbital characteristics point to a long-period comet with a period of about 500 years. This nameless visitor deposited a dense, narrow ribbon of debris in the distant past with a half-width of only around 55,000 kilometers, equal to the distance from the center of Earth to the geostationary satellite belt.

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