March 4, 1997
Available data All data used for the trajectory construction are visual observations of causal eyewitnesses. The fireball was seen by Marco Antonio Gonzalez, an amateur astronomer in Villa Nueva, Guatemala, who drew the path relative to stars and gave additional information. Other data were obtained by interviewing local people at the sites where they saw the fireball. The indicated positions on the fireball path were normally measured by a compass and an elevation measuring device. A 7 degree magnetic correction was added to the compass data.
In addition to the Gonzalez' observation, another two good observations from rather distant sites, San Pedro Sula and Comayagua, were obtained. These three observations provided a general characteristics of the fireball trajectory, i.e. the movement from the South to the North with a relatively small slope. Most of other data were obtained from people located near the trajectory. Here the fireball was extremely bright and moving high in the sky. Under these conditions many people did not remember the trajectory well a are giving almost random directions. Large selection of the data was needed. Only the data consistent with the general characteristics of the trajectory were used for the trajectory refinement. From 105 measurements obtained, only 32 were used in the final calculation. Fortunately, the sites are well spread around the trajectory and restrict the possible solutions rather well.
Only the fireball observations were used for trajectory computation. Indirect evidences (e.g. sound directions) were not used. The straight least-squares method of Borovicka (1990, Bull. Astron. Inst. Czech. 41, 391) was used for the computation.
the apparent radiant:
azimuth = 357 deg +/- 10 deg (astronomical)
zenith distance = 71 deg +/- 5 deg
right ascension = 39 deg +/- 17 deg
declination = -55 deg +/- 5 deg
the end of the luminous trajectory:
longitude = -88 deg 52.4' +/- 1.5'
latitude = +15 deg 17' +/- 2'
height = 11 km +/- 3 km
The fireball was first noticed at the height of about 70 km at -88 deg 48' W and 13 deg 49' N. It then moved to the North with a slope of about 19 deg to the horizontal. Several people noticed severe fragmentation near the end of the trajectory. According to our estimates the fragmentation occurred at the height of 15 km at -88 deg 52' W and 15 deg 10' N. The largest piece then continued to the end point given above, where it ceased to be visible.
Gonzalez was looking into his telescope when he noticed a bright illumination. This means that the fireball was significantly brighter than the Moon at that time, probably about -14 mag. At that time, the fireball was at the height of 60 km, 200 km distant from the observer and less than 20 deg above the horizon. The correction to the atmospheric extinction and the recomputation to the 100 km distance gives -16 absolute magnitude. However, this was still the beginning of the fireball. The experience with photographic fireballs as well as the theory of fireball radiation shows that the maximum light could be reached at about 20-25 km of height, where the fireball could be at least by 3 mag but more probably by 5 magnitudes brighter than at 60 km. We therefore estimate the fireball peak brightness between -19 and -21 mag.
People located near the trajectory experienced the fireball maximum luminosity from the distance of 25 km only. The apparent magnitude may have reached -24 mag which is comparable to the Sun (-26 mag). Some people really mentioned that they were unable to follow the object for its extreme brightness. Only the non-detection of the fireball by the satellite based detectors casts some doubts on the fireball brightness.
|assumed velocity||perihelion distance||semimajor axis||inclination||argument of perihelion||ascending node|
|12.0 km/s||0.98 AU||1.1 AU||8 deg||336 deg||61.194 deg|
It can be seen that the perihelion does not depend on the velocity and certainly was between 0.98 and 0.99 AU, i.e. just inside the Earth's orbit. The semimajor axis depends on the velocity, most probably was around 1.5 AU. Inclination was almost certainly between 10 and 20 degrees. The ascending node is given by the time of collision with the Earth. In general, the orbit resembles the orbits of the Lost City (q=0.967 a=1.66 i=12.0) and Innisfree (q=0.986 a=1.87 i=12.3) photographed meteorite falls and is therefore not exceptional.
The mass of the largest survived fragment (the largest meteorite) was estimated assuming the meteoroid fragmentation at 15 km of height and a continuation of the fragment luminous path down to 11 km. The corresponding mass is about 500 kg (60 cm diameter). This is, however, rather upper limit for the largest meteorite. Subsequent fragmentation events were quite possible and the resulting mass of the meteorites can be considerably less. On the other hand, the production of meteorites of the mass of tens of kilograms is almost certain.
The most probable area for a big meteorite (500 kg, if it exists) is near the point 88 deg 53' W and 15 deg 24' N, which is in Guatemala. The meteorite would reach this point by a 1-minute dark flight starting at the end of the luminous trajectory given above. The expected velocity at the impact is 180 m/s with the angle 10 deg to the vertical. Wind was neglected in the computation.
The Honduran part is generally hilly but relatively densely populated. The south of the area has not-so-high but steep hills. The vegetation is not particularly dense here. A whistling sound was reported from the village of Santa Elena located in this part.
The largest village in the suspected area is San Antonio at 15 deg 01' N. There is a small flat area to the north of San Antonio (several square kilometers, altitude around 600 m). The region further to the North as far as the Guatemalan border is filled by the mountains in the surroundings of Cerro Azul (2300 m) and El Caribe (1700 m). Originally, this was a region of rain forest. Nowadays, the area is largely deforested, new villages are being built and cultivated fields have been formed in the mountains. Nevertheless, most of the area has rich vegetation and steep slopes inconvenient for a systematic meteorite search. Possible whistling sound was reported in La Elenciona. One man mentioned black stones found (and thrown away) near Pena Blanca.
The mountains continue on the Guatemalan side of the border as far as about 15 deg 18' N. Here the mountains are generally inhabited and hardly accessible. People live in the valley of the Motagua river further to the north. The villages are located just below the mountains. The valley is flat, wide and humid (altitude below 100 m). It is used for agriculture. There are pastures with sparse trees and banana plantations. This is the region where the largest meteorites could be expected. The area is relatively convenient for a systematic search, but none has been performed. People reported no meteorites.