January 3 – Old Names, Old Stones

Today’s Factismal: Nearly 84,000 meteorites hit the Earth every year.

Today marks the start of the Quadrantid meteor shower. This shower comes from an extinct comet in an extinct constellation, but it offers one of the most intense meteor showers available – provided that you happen to be outside when the meteors arrive. And that is harder than it sounds because, unlike other meteor showers that may peak over several days, the Quadrantids last only one night and have a peak of activity for less than two hours (naturally, those two hours come way too early in the morning). But if you do happen to catch the show, it promises to be an exciting one with many meteors and even a few fireballs.

Why is that? Because though the rocks that make up the Quadrantids are very old, they come from a comet that “died” only recently. Recently in astronomical terms, that is. The earliest known observation of the Quadrantids is less than 500 years ago, and it wasn’t until 1839 that they were recognized as an annual shower. (Compare that to the Persieds, which have been observed since Roman times.) As a result, the other planets haven’t had a chance to scatter the rocks into a broad area; instead, the debris is concentrated in a narrow cone.

And it is that debris that provides the meteorids that causes the streak of light that we variously call a meteor (small), fireball (big), or bolide (very big). Most of the debris from a comet is about the size of a grain of sand and is made up of ice or small rocks. A very few pieces can be up to the size of a fist. And very, very few can be large enough to reach the ground and form an impact crater (if they explode before hitting the ground, they just make a mess). Of course, not all of the meteors that we see come from comets; many are pieces of asteroids that have collided. And we have even found some fragments of the Moon and Mars that arrived in Antarctica as meteorites!

The Great Daylight Fireball of 1972 (Image courtesy and copyright James M. Baker)

The Great Daylight Fireball of 1972 (Image courtesy and copyright James M. Baker)

But no matter how the debris got here, it always makes for a great show as it breaks up in the atmosphere. To see tonight’s show, go outside and face north. Now stick your right hand out to the side and turn half way toward it. You are now facing northeast. If you make a fist and hold it at arm’s length, then put another fist on top of that, and one more one top of that (you may have to borrow a friend), then you’ll be looking in the best direction to see the meteors as they appear to streak out of the old constellation Quadrans Muralis (now part of Bootes, thanks to the IAU). If past shows are any indication, there should be a meteor every minute or so, with many turning into giant flaming balls of death – er, fireballs.

A meteor streaks across the Earth, as seen from the ISS (Image courtesy Ron Garan, NASA)

A meteor streaks across the Earth, as seen from the ISS (Image courtesy Ron Garan, NASA)

You can also submit your count of meteors to the International Meteor organization; they’ll use the information to help us understand how meteor showers behave:
http://www.imo.net/quadrantids2012

3 thoughts on “January 3 – Old Names, Old Stones

  1. Pingback: April 14 – Nothing but blue skies – Little facts about science

  2. Pingback: June 30 – Ka-Boom! – Little facts about science

  3. Pingback: June 30 – Ka-Boom! | Little facts about science

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