Ursids To Light Up The Night Sky This Weekend

Lee Rannals for redOrbit.com – Your Universe Online

Last weekend the night skies were lit up by the annual Geminid meteor shower. While not as brilliant and spectacular, another meteor shower is peaking this upcoming weekend, promising to give backyard astronomers a show of around 10 meteors per hour.

The annual Ursid meteor shower is expected to peak on December 21, but will be occurring from December 17 to the 25th. The shower will be appearing to radiate out of the constellation of Ursa Minor, or “little bear,” which is located in the north/northeast portion of the sky.

This shower is considered to be a lot less spectacular than showers like Geminid, but that doesn’t mean it has never had its moments. Urisids are the debris that shed from the periodic comet 8P/Tuttle, which follows a 13.5-year elliptical orbit that stretches from just inside Earth’s orbit at perihelion. Every time Tuttle swings past the Sun, it leaves behind a new trail of debris, which helps feed the annual end-of-year meteor shower.

The strongest Ursid outburst on record took place in 1945 when European observers saw 120 meteors per hour. The shower was mostly ignored by sky watchers in the 1950s, 60s and 70s, but in 1986 observers spotted another 90 meteors per hour during the December event. These outbursts occurred about six years after comet Tuttle had passed perihelion.

“Basically, when these resonant meteoroids pass Jupiter’s orbit, the planet is never there,” Peter Jenniskens, a NASA scientist at the Ames SETI Institute, said in a statement in 2000 about the shower. “So, the particles are fairly safe for a period of time. The stream as a whole can then be gently nudged [by planetary perturbations] until the meteoroids become Earth-crossers. That takes 6 centuries. Gradually the meteoroids fall behind the comet because they move in a wider orbit than the comet does. The lag accumulates and, after 6 centuries, it adds up to about 6 years.”

This year’s peak rate is predicted to be somewhere around 10 meteors per hour. The moon will also be blocking most of the show because it will be relatively bright during this year’s shower.

“It is possible that this shower produces a short-lived burst of activity every December,” Robert Lunsford, Secretary General of the International Meteor Organization said in a statement in 2000. “The Holiday season combined with poor weather and bitterly cold temperatures at this time of year in the northern hemisphere may explain why Ursid outbursts are seldom seen.”

Those who really want to capitalize on the event need to go find the darkest sky they can, miles away from city lights, and stare at the darkest part of the sky at around 90 degrees away from the radiant. This shower is primarily a Northern Hemisphere meteor shower and is not visible very far south from the equator.

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