Bright fireball from the weak June Draconids shower

A weak meteor shower, the June ro-Draconids (JRD, IAU MDC 0686), was first described in 2018 (P. Jenniskens) based on the orbital analysis of just 23 meteors from this shower. It is a meteor shower of cometary origin, with a parent body belonging to the group of long-period comets (1P/Halley), with its radiant located in the constellation Draco. Meteors from this shower are rarely observed, and bright fireballs are even rarer, such as the fireball 20240602_204346, which was observed by the cameras of the CEMeNt network (Central European Meteor Network).

The fireball 20240602_204346 was recorded by the CEMeNt network cameras on June 2, 2024, at 20h43m46.1 ± 0.1s UT. Within the CEMeNt network, the fireball was directly captured on six wide-field cameras (Fig. 1–6). The flight of the fireball was documented from stations Valašské Meziříčí SW and SE (CZ, Valašské Meziříčí Observatory), Ždánice E (CZ, Ždánice Observatory), Maruška SE (CZ, Jakub Koukal), Jablonec N (SK, Jakub Kapuš), and Partizánske NE (SK, Partizánske Observatory). Additionally, the fireball spectrum was captured by spectrographs at the Valašské Meziříčí Observatory (VM_SPSW and VM_SPSE), which are crucial for determining the chemical properties of the object.

Atmospheric Path, Radiant, and Heliocentric Orbit of the Fireball

To calculate the atmospheric trajectory of the fireball and the meteoroid’s orbit within the Solar System, recordings from stations in Valašské Meziříčí (SE and SW), Maruška SE, Ždánice E, Jablonec N, and Partizánske NE were used. These recordings were captured using the UFOCapture program, processed with UFO Analyzer, and the atmospheric and heliocentric paths calculated in UFO Orbit.

The atmospheric path began at coordinates N48.9217° E18.4652°, southeast of the village of Zliechov (SK) in the heart of the Strážovské Vrchy mountains, at an altitude of 107.0 km above Earth’s surface. The end of the atmospheric path was located at coordinates N48.7353° E18.2481°, north of Bánovce nad Bebravou (SK), at an altitude of 77.2 km (Fig. 7). The fireball reached an absolute magnitude of -6.0m at an altitude of 77.8 km and traveled a distance of 39.4 km through Earth’s atmosphere in 1.1 seconds.

The body entered Earth’s atmosphere at an ideal angle of 49.1°, with a pre-atmospheric velocity of 36.62 km/s. It was classified as a medium-speed fireball, with a geocentric velocity of 34.75 km/s. The body was associated with the June ro-Draconids meteor shower (IAU MDC 0686 JRD). Before entering Earth’s atmosphere, it traveled on a highly elongated prograde orbit (Fig. 8) with high eccentricity (e = 0.955), a significant inclination to the ecliptic plane (i = 55.73°), and a perihelion distance of q = 1.0071 AU. The body was of cometary origin, with an unknown parent body belonging to the group of long-period comets associated with 1P/Halley.

Physical Properties of the Meteoroid

To estimate the initial mass and other physical properties of the body, the heliocentric orbital elements, atmospheric trajectory, and chemical properties derived from the fireball’s spectrum (captured by the spectrographs VM_SPSW and VM_SPSE) were analyzed (Figs. 9, 10). The initial parameters of the meteoroid’s heliocentric orbit were determined using the Tisserand parameter relative to Jupiter. Based on the value of the Tisserand parameter, orbital inclination, and aphelion distance, the body can be categorized into four groups. The fireball 20240602_204346 had a Tisserand parameter of TPJ = 0.925, placing it in the HT group—meteoroids of cometary origin with a long-period parent body (group 1P/Halley). According to the KB parameter (6.785), which is a function of material properties and surface temperature, the body belongs to the C2 group (common long-period cometary bodies). The PE parameter (-5.564) further classifies the fireball into the IIIAi group (also typical long-period cometary bodies).

Using parameters that characterize the shape, velocity, and other properties of the body, the initial mass was calculated. The dynamical entry mass (md) and the photometric entry mass (mf) were determined. The initial dynamical mass of the meteoroid before entering Earth’s atmosphere was only 0.047 kg. The fragmentation strength of the meteoroid was calculated based on the equality of dynamic pressure and the strength of the body at the moment of fragmentation. Atmospheric parameters at the altitude of fragmentation were modeled using NRLMSISE-00 (2002). The moment of fragmentation was determined from the absolute brightness values recorded at the Maruška SE station. The fragmentation strength of the main part of the body was 0.022 MPa, classifying it as a typical cometary body. The mineralogical density of the body (1.28 g/cm³) further supports the conclusion that the fireball 20240602_204346 originated from a common cometary particle.

The spectrum of the fireball 20240602_204346 was recorded by the VM_SPSE and VM_SPSW spectrographs; unfortunately, both recordings were affected by fog around Valašské Meziříčí following intense thunderstorms. Therefore, only the final frame of the spectrum, which included the terminal explosion of the body, could be analyzed. Both spectra exhibited superimposed ionized emission lines (e.g., MgII, FeII), meteor trail-specific emission lines (iron multiplets FeI-1, 2, and 3), and common emission lines such as FeI, CrI, and AlI. The intensity of atmospheric component emission lines corresponded to a combination of dynamic and static parts of the spectrum but was not dominant. In the NIR (near-infrared) part of the spectrum, ionized calcium lines (multiplet CaII-2) were dominant, whereas in the NUV (near-ultraviolet) region, CaII-1 lines were not dominant due to superposition with aluminum lines (multiplet AlI-1).

Acknowledgments

Acknowledgments go to all operators and station owners of the CEMeNt network. Special thanks to all institutions supporting the activities and growth of the network. The RPOS project (Development of Cross-Border Observation Network) was co-financed by the Small Projects Fund of the Interreg V-A Slovakia–Czech Republic 2014–2020 program, call code 5/FMP/11b, reg. no. CZ/FMP/11b/05/058. The KOSOAP (Cooperating Network for Astronomical Expert Observation Programs) and RPKS (Development of a Cross-Border Cooperating Network for Expert Work and Education) projects were carried out by the Valašské Meziříčí Observatory (CZ) and Kysucké Nové Mesto Observatory (SK) in cooperation with SMPH (Society for Interplanetary Matter). These projects were co-financed by the Microprojects Fund of the Cross-Border Cooperation Operational Program Slovakia–Czech Republic 2007–2013. The project for purchasing and operating high-resolution spectroscopic cameras was partially funded by the Regional Cooperation Program of the Czech Academy of Sciences, reg. no. R200402101, and the APVV-0517-12 grant (FMFI UK). The purchase of equipment at the Valašské Meziříčí Observatory was also supported by DEZA, a.s., and CS CABOT, spol. s r.o.