A particularly bright meteor seen in the skies of Earth on July 31 has been tracked back to a comet that created a field of debris when it began to disintegrate thousands of years ago.
Scientists believe that the fragment that ended its life as a fireball over Madrid, Spain, began its existence as part of Comet 169P/NEAT, which formed at the same time as the solar system, around 4.6 billion years ago. The comet, an icy body that sheds debris as it travels, is responsible for the Alpha Capricornids annual meteor shower, which first occurred between 3,500 and 5,000 years ago when around half of Comet 169P/NEAT disintegrated.
Although the small fragment and the light show created when it was destroyed in Earth's atmosphere presented no danger, the European Space Agency (ESA) pointed out in a statement that the meteor is a "cautionary tale." This is because showers of tiny fragments are left by larger bodies that once passed close to our planet, and could do so again.
When the mostly icy body of a comet passes the sun, its ices begin to change immediately to gas in a process called sublimation. The sublimation throws out into space a stream of ancient material — unchanged since the birth of the solar system — that lingers in space.
On July 31 this particular icy fragment, which astronomers believe measured around 4 inches (10 centimeters) across, began to burn bright in the Earth's atmosphere around 60 miles (100 kilometers) above Madrid. It had burnt out by the time it reached around 48 miles (77 km) above the province of Guadalajara.
Scientists tracked the trajectory of the fireball using footage shot by an ESA-operated camera of the AllSky7 network in Cebreros, Spain, as well as cameras belonging to the Southwestern Europe Meteor Network (SWEMN) and other on-the-ground cameras across Europe. Thede observations allowed SWEMN researchers to trace the meteor back to its origins, revealing it came from the same source as the Alpha Capricornid meteor shower.
This meteor shower can usually be seen in the skies between July 7 and Aug. 15 each year. Although the Alpha Capricornids create only infrequent meteors — at the shower's peak about five per hour — these can be very bright, often becoming fireballs.
However, future skywatchers may be able to catch more fireballs this season. Scientists expect the Alpha Capricornids meteor shower to become stronger over the coming centuries as more material left behind by the comet drifts into the Earth's orbit. According to ESA, by the year 2220 the Alpha Capricornids will be stronger than any current annual meteor shower that Earth experiences.
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Robert Lea is a science journalist in the U.K. whose articles have been published in Physics World, New Scientist, Astronomy Magazine, All About Space, Newsweek and ZME Science. He also writes about science communication for Elsevier and the European Journal of Physics. Rob holds a bachelor of science degree in physics and astronomy from the U.K.’s Open University. Follow him on Twitter @sciencef1rst.