On May 30, 2017, at about 21 h 09 min 17 s UTC a green bright fireball crossed the sky of north-eastern Italy. The fireball path was observed from some all-sky cameras starting from a mean altitude of 81.1±0.2 km (Lat. 44.369^o±0.002^o N; Long. 11.859^o±0.002^o E) and extinct at 23.3±0.2 km (Lat. 45.246^o±0.002^o N; Long. 12.046^o±0.002^o E), between the Italian cities of Venice and Padua. In this paper, on the basis of simple physical models, we will compute the atmospheric trajectory, analyze the meteoroid atmospheric dynamics, the dark flight phase (with the strewn field) and compute the best heliocentric orbit of the progenitor body. Search for meteorites on the ground has not produced any results so far.

A map from Google Earth showing the distribution of PRISMA stations on April 2019. Most of the stations are concentrated in northern Italy. Legend: dark dots = working camera; gray/white dots = setup phase.

A Google Earth map showing the position of the stations listed in Table 1 and the fireball trajectory projected on the ground.

A negative image showing the full path of IT20170530 from Rovigo. North is down, South is up. The bright object on the left is the Moon near the western horizon. The fireball moved from top left to bottom right. The total duration of the fireball was about 9.51 s. From this image, no significant fragmentation of the meteoroid appears.

A Google Earth map showing the best trajectories, both in atmosphere and projected on the ground, resulting from the triangulation between PRISMA-Rovigo, IMTN-Casteggio and IMTN-Contigliano.

Fireball height versus time as a result of the triangulation from Rovigo, Contigliano and Casteggio. Gray dots = observed values; dotted line = model with starting guess values; black line = best fit model.

Residual between the observed height versus time values and the dynamical model of the meteoroid (Rovigo, Contigliano and Casteggio). The mean residual value is about 0.12 km, discussion in the text.

Fireball velocity versus time as a result of the triangulation from Rovigo, Contigliano and Casteggio. The speed is computed using Rovigo’s temporal data only. The initial dispersion of the points is due to the fact that the fireball was very far from the station and the displacement was low. In this condition, the sky position uncertainty is the dominant factor in the computed velocity. Gray dots = observed values; dotted black line = model with starting guess values; black line = best fit model.

Residual between the observed velocity values versus time and the dynamical model of the meteoroid (Rovigo with Contigliano and Casteggio). The mean residual value is about 0.3 km/s, discussion in the text.

Fireball velocity versus height as a result of the triangulation from Rovigo with Contigliano and Casteggio. Gray dots = observed values; dotted black line = model with starting guess values; black line = best fit model.

Fireball relative mass/(cross section) ratio versus time as a result of the triangulation from Rovigo with Contigliano and Casteggio. In this figure, it is possible to follow the meteoroid ablation versus time because M/S ∝ r, where r is the meteoroid radius. The best fit model line starts below 1 because the first observation was made when the ablation was already on. The scattering is due to the initial uncertainty on the fireball speed. Gray dots = observed values; black line = best fit model.

Fireball reference system (l, h, x) for dark flight phase. The black dot is the terminal point of the luminous path. The component velocity vl is parallel to the fireball motion direction, vx is along the orthogonal direction, and vh is toward the bottom (so vh<0 always).

Wind speed versus height in the meteoroid reference system from San Pietro Capofiume. Black line: wind along meteoroid motion direction (l axis). Wind speed values greater than zero are against meteoroid motion. Gray line: right orthogonal direction to the meteoroid motion (l_x axis). Wind speed values greater than zero are against the positive direction of v_x.

Parallel view of the residual meteoroid height versus horizontal distance along the l axis starting from the terminal point. Notice the small deformations at the end of the vertical section of the trajectory, due to the wind.

Front view of the residual meteoroid trajectory. Meteoroid height versus orthogonal distance l_x. The trajectory oscillations are in phase with the winds directions, but the orthogonal movements are a few tens of meters only.

A Google Earth maps showing the possible impact points on the ground obtained from the Monte Carlo simulation. The strewn field dimension is about 1.7 × 0.6 km, about north of the town of Bojon.

Nominal heliocentric orbit for the progenitor meteoroid of the fireball IT20170530 as seen from the ecliptic north pole. The dots symbolically represent the Main Belt. The position of the planets on their orbits is that at the time of the fireball. The fireball clones orbit are indicated in gray color.

Black dots show the NEAs with DN < 0.15 in the plane U-cosθ; the big red dot shows IT20170530. The region below the a = 8 line contains orbits bound to the Sun, and the region on the left of the i = 90^o line contains prograde orbits.