 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
| . |  |
. |
 by Staff Writers San Francisco CA (SPX) Aug 23, 2018
The bright flashes that lit up the evening skies near Detroit, Michigan earlier this year were not the only signs of the meteor that disintegrated in the atmosphere on 17 January 2018. The meteor explosion was also captured by infrasonic microphones and seismometers, offering a rare chance to compare these data with satellite and ground camera images. In a report in Seismological Research Letters, a team of scientists led by Michael Hedlin of Scripps Institution of Oceanography use these data to pinpoint the time, location and height of the bolide disintegration, and to calculate an approximate yield for the explosion. Bolides, sometimes called "fireballs," are extremely bright meteors that explode in the atmosphere. They estimate a likely yield within the range of .8 to 8.1 tons of TNT, and probably equivalent to 2.2 tons of TNT. About 2000 bolides this size or larger pass through the Earth's atmosphere each year, which makes the Michigan bolide a particularly interesting event to study, said Hedlin and colleagues. Scientists would like to know more about how frequently we can expect to see near-Earth objects of this yield, to assess the potential threat they pose on the ground. Researchers also use data from bolide bursts as "test cases" to determine how well infrasound and seismic instruments can locate and characterize secret nuclear test explosions. Other bolides such as the February 2013 Chelyabinsk, Russia fireball also have been studied intensively through infrasound, seismic and optical observations - and made famous through "dashcam" videos taken by Russian drivers. But "it's pretty unusual for such immense events to occur over a heavily instrumented area; they could be expected to occur once every several decades," said Hedlin. When the Michigan bolide traveled through and exploded in Earth's lower atmosphere, it produced large shock waves and a variety of soundwaves, including waves in the low-frequency or infrasound range below 20 hertz. These waves were detected by infrasound microphones at seismic stations in the Central and Eastern US Network (CEUSN), deployed through the eastern half of the continental United States. The researchers were also able to detect the burst in seismic wave data collected by seven stations in Michigan, Ohio and Ontario. Hedlin and colleagues made calculations from these data to determine the location, height, timing and yield of the bolide's disintegration. They were able to compare these values with the "ground truth" for these characteristics as calculated by optical observations of the bolide taken from numerous cameras on the ground and from recordings by the Geostationary Lightning Mapper instrument on a National Oceanic and Atmospheric Administration (NOAA) satellite. The infrasound and seismic calculations were consistent with the optical observations, the researchers concluded, although some of the calculations - such as the location and yield provided by infrasound data - contained a large amount of statistical uncertainty. The seismic data, however, were able to pinpoint the location and height of the burst within kilometers, in agreement with the optical data. If the Michigan bolide is the smallest detectable event that can be measured using CEUSN data, researchers should be able to detect about 15 events of this size or larger each year in eastern North America, Hedlin and his colleagues write. The Michigan analysis could also help researchers who study clandestine nuclear tests "make some inferences about how detectable similar-sized anthropogenic events would be - how far away from the explosion source we'd be able to detect signals, for example," said Hedlin.
"Great Show" predicted for Perseid meteor peak on August 12-13 Boston MA (SPX) Aug 07, 2018 The Perseid meteor shower, an annual celestial event beloved by millions of skywatchers around the world, is about to make its annual return to the night sky. And thanks to a new Moon, there'll be no bright moonlight to hinder the view. Sky and Telescope magazine predicts that this year's Perseid shower will reach its peak on Sunday night, August 12th, and early morning on the 13th. You will also see some Perseids, though fewer in number, for several nights before and after that date. "The m ... read more
|
|||||||||||||
|
|
| The content herein, unless otherwise known to be public domain, are Copyright 1995-2024 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. General Data Protection Regulation (GDPR) Statement Our advertisers use various cookies and the like to deliver the best ad banner available at one time. All network advertising suppliers have GDPR policies (Legitimate Interest) that conform with EU regulations for data collection. By using our websites you consent to cookie based advertising. If you do not agree with this then you must stop using the websites from May 25, 2018. Privacy Statement. Additional information can be found here at About Us. |
del.icio.us
Digg
Reddit
Google
