Free Astronomy Magazine November-December 2014

SMALL BODIES can be associated with certainty to meteoritic showers. There is one particular case that has challenged the stubbornness of researchers, because even though it is the best scientifically documented event in history, it took a good 20 years to uncover its traces on the ground. We refer to the Benešov bolide, which on 7 May 1991 fell almost ver- tically on the eponymous place in the Czech Republic, about forty miles south-east of Prague. On that occurrence, in the Czech Republic were fortunately active three sta- tions of the European Fireball Net- work (Ond ř ejov, Tel č e P ř imda), equipped with four all-sky cameras (3 with rotating shutter were fixed and 1 guided) and two spectral cam- eras. The recordings of the event on photographic plates made it possi- ble to estimate at about -21 the mag- nitude of the bolide, at least from the Ond ř ejov station, distant just 32 km from the falling meteoroid, in the instant of maximum brilliance announcing its fragmentation. Such high brightness caused the overex- posure on the plates of the bolide trajectory making it impossible to take full advantage of the rotating shutters to cal- culate the speed of the object, as the typi- cal segments they created on the image were visible only at the start and end of the trajectory. During the years following the fall, several scientific papers were pub- lished on the bolide, mostly by Czech re- searchers, but even though some of them had indicated with apparent certainty the places where pos- sible fragments of the meteoroid may be recovered, all ground search attempts led to nothing signifi- cant. Yet a number of me- teorites must have necessarily reached the ground. A con- viction that arose from the analysis of the spectral record- T he Benešov bolide photo- graphed at mid- night on 7 May 1991, from an all- sky camera of the European Firball Network. Left, an enlargement of the luminous track, with indi- cated the point where the explo- sion of the me- teoroid occurred, at an altitude of about 24 km. [Astronomický ústav Akademie v ě d]