M20160511-210400

This fireball over Middle Finland close to local DST midnight resulted in more than a hundred visual reports to our Taivaanvahti, and this was captured on about 8 cameras.
The entry track is derived by means of mainly two quite nearby (to the fireball) and mutually favorably situated cameras of Mikkeli and Joutsa.

The Mikkeli image by Aki Taavitsainen and Jani Lauanne is seen in this, above.

It is difficult to measure the brightness of the flash but this may be around –15, possibly more bright as seen from Mikkeli.

The fireball arrived from azimuth direction of 192 with the slope of 29 degrees.
The entry velocity was 16.8 km/s. The beginning of luminous flight was at the height of 87 km and the terminal height at 29 km at the velocity of 4.2 km/s.

The bright flash was at the height of 44 or 45 km. Then the dynamic pressure was only about 4 kp/cm2.

Assuming that a constant ablation coefficient during the flight would give 0.031 s2/km2,  which is quite big and more or less which is the result of fragmentations.

The entry mass was derived around 10 kg and the main fragment in the end, something like 150 or 200 g. Considering the brightness and relatively modest velocity this is quite small, but consistent to the big ablation coefficient. In total there may be several more smaller fragments of this. These mass-values are valid for a normal chondrite density assumption. If the density were smaller, then these values would get bigger. The main fragment might be around half a kg.

The solar system orbit is in between 0.90 and 3.93 au. And the special thing in this is the very small inclination of the orbit. This was derived as 0.02 degrees. Actually the uncertainty is bigger than this value, so it is not even known on which side of the Sun the ascending node is. Longitude of perihelion is 275.1 degrees.

Another image of this fireball can be found at http://www.taivaanvahti.fi/observations/show/52873