Atmospheric trajectory of bright fireball from the morning of 29 January 2021
On Friday, January 29, 2021, shortly after 7 a.m. (between 7:04:54 and 07:04:58 CET), a bright meteor (fireball) appeared over central Europe. In a part of the Czech Republic, sounic booms were heard few minutes later. Most of Czech territory was covered with thick clouds at that time, and it was already dawning. Nevertheless, a number of witnesses reported sightings of bright flashes through the clouds and subsequent sounds similar to thunder. It was obvious that this was a really significant fireball. The radiometers at our two westernmost stations, which were the only ones still working before full light, recorded a detailed light curve of the fireball. Unfortunately, due to unfavourable weather, none of our cameras, including video cameras that are in operation also during the daylight, captured a direct image of the fireball. We have therefore asked the public for help in finding any incidental footage. We knew from eyewitnesses that the fireball was visible through thinner cloud layers in the extreme north of Bohemia and also in the vicinity of České Budějovice (Southern Bohemia).
First of all, we must thank all the observers and owners of the security cameras who provided us with their observations and video recordings. From the Czech Republic, we received security camera footage from seven different locations. The recordings show the brightening of the sky and the surrounding landscape, and in two cases, the sound was also recorded few minutes after the fireball. We also found the flash in the clouds on two cameras that transmit live image to the internet and allow users to view the footage 12 hours back in history (Janova hora, and Lomnice nad Popelkou). Unfortunately, we did not find any direct record of the fireball from the Czech Republic, so it was necessary to search for records in the surrounding countries as well.
Several fireball footage quickly appeared on the internet after the fireball passage, including footage from on-board car cameras (dash cameras), security cameras, and weather cameras. It was important to continuously find these videos and try to get them calibrated using the starry sky.
In the Czech Republic, Lukáš Ronge (Amateur Meteorological Society) helped us find video recordings on the internet. In Poland, the same was done by Jarosław Morys (Polish Meteorite Society), who also found GPS locations of several videos and obtained the original fireball records and star recordings necessary for calibration for us. The following people contributed very willingly to calibrate two videos from Poland (near Poznań - from the 33rd second of compilation, and near Swiebodzin): Tomasz Kluwak (Lusówko Platanus Observatory), Justyna Gołębiowska and Agnieszka Kryszczyńska (Adam Mickiewicz University in Poznań), and Paweł F. Matysiak (photographer) calibrated the first video; Mateusz Daszuta and Marek Marcinkowski (Kepler Science Center - Planetarium Venus, Zielona Góra) calibrated the second video. Both of these calibrations were negotiated for us by Tadeusz Jopek (Adam Mickiewicz University in Poznan). Tomasz Kluwak also obtained two videos that are not available on the internet. In Germany, there are several records from moving cars and also a footage from the Lindenberg Observatory. The original records and records of stars for calibration were provided to us by the observatory operator André Knöfel. We would like to thank all of the above mentioned person once again for the data they provided and the time they devoted to the work needed to determine the trajectory of this fireball. Our thanks also go to the camera owners who shared their recordings on the internet.
Below is the description of the fireball trajectory as determined by us based on the video footage obtained. We used the following videos for the final determination of the atmospheric trajectory:
Szczecin – Łasztownia: from the 26th second https://www.youtube.com/watch?v=6Qf_M1lxWs0
Kalwy: from the 28th second https://www.youtube.com/watch?v=YOZiQX-aI9k
Sady, Poznań: from the 33th second https://www.youtube.com/watch?v=YOZiQX-aI9k
The combination of the above video recordings and the fireball light curve known from our two cameras at Šindelová (Ore Mountains) and Přimda (Czech Forest Mountains) stations allow us to describe the fireball as follows. At 7:04:53 Central European time, a meteoroid weighing approximately 45 kilograms entered the Earth's atmosphere at an altitude of 88.5 km above the Ore Mountains (Přísečnice reservoir near the border with Germany). At that time, the body was moving at a speed of almost 33 km/s along a track inclined 29 degrees to the surface and directed to the east-southeast. In the last one third of the trajectory, there were several significant flares during which the original body disintegrated. These explosions at altitudes between 47 and 29 km above the ground also contributed to generating sonic booms reported by many witnesses. The maximum brightness of about twenty times the brightness of the full Moon (almost -16 magnitude) was reached by the fireball at an altitude of 34.5 km northwest of Neratovice (above the village of Obříství). The body suddenly disappeared after 3.8 seconds of luminous flight after a flare at an altitude of 29.5 km above the village of Všetaty, when its speed dropped just below 20 km/s. Based on the fireball radiation and its speed, it can be determined that only a very small part of the original mass could have survived the flight. The vast majority of the material was consumed during the flight. If there was a meteorite fall, the weight of the meteorites will be in the order of units of grams in the maximum, and their number will be relatively small. In this case, the high brightness of the fireball and the high intensity of sonic booms were mainly caused by the high initial speed of the meteoroid. On the other hand, the high speed and the associated high pressure stress caused the body to almost completely crumble to dust. In typical meteorite falls, the entry speed tends to be significantly lower, usually below 20 km/s. A systematic search for meteorites does not give much hope to a successful find in this case. The projection of the atmospheric trajectory to the surface is shown in the figure.
Before the collision with the Earth, this meteoroid with a diameter of about 30 cm orbited the Sun along an elliptical orbit inclined 20 degrees to the plane of the ecliptic, i.e. the plane of the Earth's orbit. In the perihelion, the meteoroid approached the Sun almost as close as Mercury. This fact, together with a relatively high inclination, caused the high collision velocity with the Earth. In the aphelion, the meteoroid entered the outer part of the main belt of asteroids located between the planets Mars and Jupiter. The meteoroid therefore most likely represented a small part of a main belt asteroid.
Lukáš Shrbený, Jiří Borovička, and Pavel Spurný - Astronomical Institute of the CAS, Ondřejov