quinta-feira, 30 de outubro de 2008

Fireball captured by Canadian cameras

Posted: October 28, 2008For the second time this year The University of Western Ontario's Meteor Group has captured rare footage of a meteor streaking across the sky and possibly falling to the ground.
The meteor was tracked by all seven of Western's Southern Ontario Meteor Network cameras at 5:28 am on Wednesday 15 October, local time. Western University astronomers suspect that some fraction of the meteor may have fallen to the ground, amounting to a few hundred grams in mass.

All seven cameras of the Meteor Network spotted this meteor streaking across the sky; this image was taken by the Orangeville camera number 6. The lights at the bottom are a moving aircraft. Video of the meteor is available here. Image: University of Western Ontario.

By studying the video footage, the astronomers concluded that the meteor penetrated the Earth's atmosphere at an altitude of around 37 kilometres whereupon it slowed down considerably. Most meteoroids burn up by the time they hit an altitude of 60-70 kilometres from the ground, but in this case, one or more small meteorites could have made it to the ground intact. The surviving fragments are predicted to lie in a region north of Guelph. The trajectory of the meteor could also be tracked back to its pre-impact orbit, putting it into the typical Earth crossing asteroid type of a stony meteorite. Stony meteorites are composed mostly of silicate minerals and account for around 95 percent of all meteorites seen to fall to Earth.
In March, the same network of all-sky cameras captured a meteor careering towards the Parry Sound area. All-sky cameras consist of a fish eye lens that enables the whole sky to be imaged at once, as the name suggests. A network of three or more cameras allows the meteors to be located via triangulation.

The fireball is suspected to have shed meteorites in a region north of Guelph. Residents are encouraged to contact researchers at Western if they witnessed the event or if they have found fragments of the meteorite. Image: University of Western Ontario.

Just a week before the Canadian accomplishment, a three-metre wide asteroid was seen powering through the skies of northern Sudan as a glowing fireball (read our report here). Meteors streak across the sky on a daily basis, and when the Earth passes through the tail of a comet, we are treated to a meteor shower, such as the Perseids, Orionids, Leonids and Geminids, which offer the best displays. However, it is quite rare that meteoritic material reaches the ground intact, but finding this treasure allows scientists to sample the material of an extraterrestrial body, teaching us about the composition of the residents of our cosmic neighbourhood. The three-metre wide asteroid was a reminder that the Earth is also at risk from potentially devasting impacts without much notice, indeed, that case study was detected less than a day before it was due to penetrate the Earth's atmosphere.

Lucimary Vargas
Observatório Astronômico Monoceros
Além Paraíba-MG-Brasil

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