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Andromedids: See a forgotten meteor shower caused by a dead comet this weekend

A colour lithograph from 1877 depicts the Andromedid meteor shower of 1872

Antiqua Print Gallery/Alamy

A “lost” meteor shower may surprise skywatchers this weekend, astronomers have found, with the potential for as many as 200 meteors per hour on 2 December.

The shower in question is the Andromedids, which is caused by dust and rocks left behind by the comet 3D/Biela entering Earth’s atmosphere and burning up. In most years the Andromedids barely produce more meteors than you might expect on an average evening of stargazing. But every so often, they kick off.

Records show that the Andromedids in 1872 and 1885 were particularly spectacular, with more than 1000 meteors in an hour. The last time the shower was active was in 2011, producing about 50 meteors per hour.

The reason for this inconsistency is the death of comet 3D/Biela. It was first spotted in 1772, and then again in the mid-1800s, when it had split into two pieces, but it has never been seen again. It seems to have disintegrated, which caused the particularly bright showers in the late 1800s.

But there is still a trail of debris and dust left behind by the comet’s original path, which Earth, on occasion, finds itself flying through. This happens rarely because the remaining material moves along orbits similar to the comet’s path. “It takes the meteoroids 6.7 years to orbit the sun,” says Robert Weryk at the University of Hawaiʻi at Mānoa. “Earth is rarely in the same place at the same time.”

This year could be one of those times. In a paper in 2012, astronomers from the University of Western Ontario in Canada, including Weryk, simulated the movement of the dust trail. The model predicted we could be in for as many as 200 meteors per hour, peaking on 2 December.

Last year, the astronomers started working on a refined model, and found the new one disagrees with the original prediction of a strong outburst this year. “The critical factor is the orbital trajectory of the comet in the 1600s,” says Paul Wiegert, who led the research. “We have to extrapolate backwards in time to determine its earlier position, and the effect of forces due to cometary jets is very hard to predict.”

Nevertheless, Wiegert is looking forward to watching for the outburst. “All our available meteor detections equipment, cameras and radar, is watching in anticipation,” he says.

To see the meteor shower yourself, you don’t need any equipment. The Andromedids is named after Andromeda, the constellation from which the particularly bright displays in the 1800s appeared to come from. But this year, the meteors are expected to radiate from nearby Cassiopeia.

You don’t have to know how to find Cassiopeia to see the shower, but it is an easy constellation to spot. If you do want to look in this direction though, no matter where or when you are looking, a good place to start is by facing north – Cassiopeia won’t be far away. It is a small, distinctive W or M shaped group of five brights stars. The best time to watch meteor showers is usually after midnight, wherever you are.


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