February tends to be a quiet month for fireball reports : the background meteor rates are generally low in the first half of the year, the UK weather is often unhelpful (many parts of the UK had a rather cloudy February 2013) and the low outside temperatures encourage people to stay indoors.<\/p>\n
Steve Cares<\/strong>s<\/strong>\u00a0(Grantham, Lincs) reported a mag -5 white fireball seen in the NNW sky while driving at\u00a004:31 GMT<\/strong>\u00a0on\u00a0Feb 6<\/strong>.<\/p>\n Philip Symons<\/strong>\u00a0(Stanwell, Surrey, near Heathrow) reported a possible mag -7 fireball seen at\u00a018:44 GMT on Feb 15<\/strong>. A check of the University of Hertfordshire all-sky cameras found that the Niton (Isle of Wight) camera wasn’t operating at the time and the Bayfordbury (Hertfordshire) camera was clouded out. However, there is\u00a0something bright seen through the cloud in the image that starts at \u00a018:37:43 (see\u00a0star.herts.ac.uk\/allsky\/imageget.php<\/a>\u00a0)\u00a0.<\/p>\n The reported duration of 35 seconds was unusually long for a fireball – the lack of other reports of this object probably indicates that this was not a fireball,\u00a0but a more local that strongly resembled a fireball<\/p>\n Any further sightings of these or different fireballs (meteors of magnitude -3 and brighter) would be welcomed by the Meteor Section.<\/p>\n Advice on what to record and where to report to \u00a0can be found at :\u00a0www.popastro.com\/meteor\/fireballs\/makingobservations\/index.php<\/a><\/p>\n Chelyabinsk fireball of 2013 Feb 15\u00a0<\/strong><\/u><\/p>\n This fireball appeared at\u00a009:20 local time\u00a0<\/strong>(03:20 GMT<\/strong>) over the city of Chelyabinsk, which lies close to Russia’s border with Kazakhstan. Unlike the mini-asteroid\u00a02008 TC3 (which entered the atmosphere over Sudan in October 2008), the object wasn\u2019t detected in advance due to its \u201csmall\u201d size and due to its final approach to\u00a0the Earth being from a direction within 15 degrees of the Sun.<\/p>\n Given the magnitude of the event it soon became worldwide news, especially with attention already being directed to the predicted close encounter later that day\u00a0with asteroid 2012 DA14. Despite some wild claims that the Chelyabinsk object was a fragment of 2012 DA14, the two objects were not related. 2012 DA14 was\u00a0approaching the Earth from the south (effectively from a radiant close to declination -81 degrees) and so was well below the horizon from Chelyabinsk (Lat 55 N).\u00a0The object that produced the Chelyabinsk fireball was, in contrast, approaching from the east (from the constellation of Pegasus) and so two orbits were very\u00a0different.<\/p>\n There are many on-line reports of the Chelyabinsk fireball, including<\/p>\n www.nasa.gov\/mission_pages\/asteroids\/news\/asteroid20130215.html<\/a><\/p>\n rt.com\/news\/meteorite-crash-urals-chelyabinsk-283\/<\/a><\/p>\n www.bbc.co.uk\/news\/world-europe-21468116<\/a><\/p>\n apod.nasa.gov\/apod\/ap130223.html<\/a><\/p>\n Some early reports referred to this event as a “meteor shower”. This is inaccurate as it was a single object entering the atmosphere.<\/p>\n Some other early reports even claimed that the Russian military had shot it down. However, given that the event lasted only around 30 seconds after entering the Earth’s\u00a0atmosphere, it would have required an unbelievably rapid response to launch a missile to intercept it is such a short time !<\/p>\n There were also suggestions that had the object arrived several hours later that it would have occurred over northern England. This is not true of course as by\u00a0then the Earth would have moved further around its orbit and therefore the object would have missed the Earth.<\/p>\n Making\u00a0magnitude<\/strong>\u00a0estimates of \u201croutine\u201d fireballs can be tricky. For bright objects such as this it is much harder. However, inspections of shadows in videos\u00a0suggested that the object was brighter than the Sun.<\/p>\n In order to work out the\u00a0atmospheric trajectory<\/strong>\u00a0of the fireball and the former solar system orbit of the parent object, it is necessary to have access to images\u00a0or videos of the fireball from several well-separated locations. We were fortunate therefore in that the fireball appeared in the daytime over a populated area\u00a0and that in this area many drivers have\u00a0video cameras<\/strong>\u00a0fitted that show the view through their car windscreens. It is also straightforward nowadays to upload\u00a0images to\u00a0social media<\/strong>\u00a0such as Facebook. Had the fireball occurred 20 years earlier, such images would have been less readily available. Had the event occurred at\u00a0the height of the Cold War (or in 2013 over Korea), we have to wonder about how the event could have been misinterpreted … \u00a0Fortunately, the Cold War came to an\u00a0end and some of the most useful information about the object actually came from a network of\u00a0infrasound sensors<\/strong>operated by the Comprehensive Test Ban Treaty\u00a0Organization (CTBTO).<\/p>\n Early analyses soon showed that the fireball achieved its\u00a0maximum brightness<\/strong>\u00a0just south of Chelyabinsk, Russia, at an\u00a0altitude<\/strong>\u00a0of\u00a023.3 km<\/strong>\u00a0(14.5 miles) approx\u00a013\u00a0seconds<\/strong>\u00a0after entering the atmosphere and was travelling at a\u00a0velocity of 18.6 km\/s<\/strong>\u00a0(11.6 miles\/sec) at the time.\u00a0Infrasound data<\/strong>\u00a0indicates that the event, from\u00a0atmospheric entry to the meteor’s airborne disintegration took\u00a032.5 second<\/strong>s. The estimated\u00a0size<\/strong>\u00a0of the object, prior to entering Earth’s atmosphere, was approx\u00a017\u00a0metres<\/strong>\u00a0(55 feet). Its\u00a0estimated mass<\/strong>\u00a0was\u00a010,000 tons<\/strong>\u00a0and the\u00a0energy released<\/strong>\u00a0during the event was equivalent to\u00a0nearly 500 kilotons of TNT<\/strong>, making it the biggest\u00a0event since that of Tunguska in June 1908. It was fortunate in that the object entered the atmosphere at a\u00a0fairly shallow (16-20 deg) angle<\/strong>\u00a0and therefore much\u00a0of its energy was absorbed without it penetrating to a lower altitude. Nevertheless, over a thousand people needed medical attention, mostly resulting from the\u00a0blast wave which arrived several minutes after the fireball. By this time people were looking out through windows and were consequently hit by fragments of glass\u00a0when the blast wave shattered the windows.<\/p>\n Recovering\u00a0meteorite fragments<\/strong>\u00a0that have reached the Earth\u2019s surface is usually not straightforward \u2013 most black rocks lying on the ground are terrestrial rocks\u00a0rather than meteorites. However, in this case, the ground was covered in snow and the smaller fragments were either lying on top of the snow or encased within it,\u00a0whereas terrestrial black rocks would be buried under the snow.<\/p>\n","protected":false},"excerpt":{"rendered":" February tends to be a quiet month for fireball reports : the background meteor rates are generally low in the first half of the year, the UK weather is often unhelpful (many parts of the UK had a rather cloudyRead more<\/span><\/a><\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"footnotes":""},"categories":[6],"tags":[],"class_list":["post-2963","post","type-post","status-publish","format-standard","hentry","category-meteor-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t