Free Astronomy Magazine November-December 2014

SMALL BODIES on rough terrain. But the his- torical group of researchers involved in the study of the Benešov bolide (among which Pavel Spurný and Ji ř í Boro- vi č ka −Astronomical Institute of the Academy of Sciences of the Czech Republic− stood out for their tenacity) had never given up trying to find the elusive fragments, until in February 2011 came the turning point, thanks to the complete re-examination of the old re-cordings of the event. Trough the high-reso- lution digitalization of the images, the application of new research techniques and the knowledge gained in the study of re- cent bolides (which have shown how dur- ing those events fragments of any size and weight are in fact formed, from dust grains to pieces of several kilograms), astrono- mers were able to improve the accuracy of all the basic parameters of the event, in-clu- ding those seemingly obvious, such as the geographical location of the stations, pro- ved wrong by 10-20 metres in latitude and longitude, and the time referred to the central phase of the event, set at 23:03:46 UT (GMT). This shifts forward by 7 seconds that estimated in 1991, with a resulting lengthening of the bolide trajectory (from 70160 metres to 70550 metres, with the start of the event at 89126 metres of alti- tude and end of the same at 19493 metres) and consequential increase of its speed, now set at more than 21 km/s. This new speed in turn affects the original orbit of the meteoroid, which was found to have its perihelion inside the Earth's orbit and aphelion in the main asteroid belt, where the object being discussed was probably formed as a result of a collision between larger size objects. Inevitably, all T op and bot- tom, the two trajectories of the bolide calculated after 20 years and projected to the ground. During this time the area has undergone heavy changes. Left, J. Borovi č ka and H. Zichová, photographed the day before find- ing the third piece of the Benešov meteorite. [Spurný et al./M. Janá č ]