|Posted on Aug 12, 2010 12:42:22 AM | William Cooke | 0 Comments ||
Real-life meteor showers are not like what you see in movies -- there are no flaming rocks barreling out of the sky blasting holes in buildings, or sending cars hurling many yards through the air. Most meteor showers are caused by debris left behind by comets, icy particles mixed with dust and organics that stand no chance of surviving their kamikaze death dives through Earth's atmosphere. The meteors that actually do make it through, becoming meteorites when they strike ground, are very, very few in number and originate from asteroids (and much more rarely, Mars and the Moon). There are only a handful of recorded falls each year.
So how low can a Perseid get? The NASA all-sky cameras can provide the answer, at least for the bigger Perseids (inch or so across); the smaller particles burn up higher. Our two station camera network can determine the trajectory of a meteor through triangulation, and tell us the start height of the meteor (the location where it is first seen) and its end height (the location where it disappears or "burns up"). Both cameras observed 80 Perseids last year and 24 so far this year, which gives us enough data to tackle the problem.
We start out by taking the end heights of the Perseids and throwing them into 1 mile wide altitude bins. This results in the following graph:
Looking at the plot, it is apparent that most large Perseids burn up at about 56 miles (90 km) altitude. Some ablate as high as 65 miles (104 km), whereas others may get as low as 47 miles (76 km) altitude. We see none getting down to 45 miles or lower, which gives this old ground dweller a warm fuzzy feeling -- I can enjoy the shower, secure in the knowledge that the meteors are going poof way up there.
It turns out that our friends the Perseids don't get very low at all, ending their interplanetary journeys at least 46 miles above our heads.
Tags : Bill Cooke, Marshall Space Flight Center, Perseids, meteor shower