Taurid meteor shower produces prolonged but usually low activity every October and November. In some years, however, the activity is significantly enhanced. Previous studies based on long-term ...activity statistics concluded that the enhancement is caused by a swarm of meteoroids locked in 7:2 resonance with Jupiter. Here we present precise data on 144 Taurid fireballs observed by new digital cameras of the European Fireball Network in the enhanced activity year 2015. Orbits of 113 fireballs show common characteristics and form together a well defined orbital structure, which we call new branch and which was evidently responsible for the enhanced activity. This new branch is part of Southern Taurids and was encountered by the Earth between October 25 and November 17. We found that this branch is characterized by longitudes of perihelia lying between 155.9–160° and latitudes of perihelia between 4.2–5.7°. Semimajor axes are between 2.23–2.28 AU and indeed overlap with the 7:2 resonance. Eccentricities are in wide range 0.80–0.90. The most eccentric orbits with lowest perihelion distances were encountered at the beginning of the activity period. The orbits form a concentric ring in the inner solar system. The masses of the observed meteoroids were in a wide range from 0.1 g to more than 1000 kg. We found that all meteoroids larger than 300 g were very fragile (type IIIB), while those smaller than 30 g were much more compact (mostly of type II and some of them even type I). Based on orbital characteristics, we argue that asteroids 2015 TX24 and 2005 UR, both of diameters 200–300 m, are direct members of the new branch. It is therefore very likely that the new branch contains also numerous still not discovered objects of decameter or even larger size. Since asteroids of sizes of tens to hundreds meters pose a threat to the ground even if they are intrinsically weak, impact hazard increases significantly when the Earth encounters the Taurid new branch every few years. Further studies leading to better description of this real source of potentially hazardous objects, which can be large enough to cause significant regional or even continental damage on the Earth, are therefore extremely important.
Asteroid 2024 BX1 was the eighth asteroid that was discovered shortly before colliding with the Earth. The associated bolide was recorded by dedicated instruments of the European Fireball Network and ...the AllSky7 network on 2024 January 21 at 0:32:38–44 UT. We report a comprehensive analysis of this instrumentally observed meteorite fall, which occurred as predicted west of Berlin, Germany. The atmospheric trajectory was quite steep, with an average slope to the Earth’s surface of 75°.6. The entry speed was 15.20 km s −1 . The heliocentric orbit calculated from the bolide data agrees very well with the asteroid data. However, the bolide was fainter than expected for a reportedly meter-sized asteroid. The absolute magnitude reached −14.4, and the entry mass was estimated to be 140 kg. The recorded bolide spectrum was low in iron, based on which, the meteorite was expected to be rich in enstatite. The recovered meteorites, called Ribbeck, were classified as aubrites. The high albedo of enstatite (E-type) asteroids can explain the size discrepancy. The asteroid was likely smaller than 0.5 meter and should rather be called a meteoroid. During the atmospheric entry, the meteoroid severely fragmented into much smaller pieces already at a height of 55 km under an aerodynamic pressure of 0.12 MPa. The primary fragments then broke up again, most frequently at heights 39−29 km (0.9–2.2 MPa). Numerous small meteorites and up to four stones larger than 100 g were expected to land. Within a few days of publication of the location of the strewn field, dozens of meteorites were found in the area we had predicted.
Aims. The complex study of millimetre-sized meteoroids can reveal more about the structure and origin of population of these meteoroids. Methods. Double-station video observations, paired with ...spectroscopic video observations, were used to study small meteoroids. In total 152 sporadic and shower meteors of maximum brightness between magnitude −5 and +3 were analysed. Spectral classification was based on time-integrated intensities of lines of Na, Mg, and Fe. Meteor light curves and deceleration were fitted by the grain erosion model. Heliocentric orbits of all meteors were computed. Monochromatic light curves were constructed in order to study differential ablation. The length of meteor wakes was evaluated as well. Results. The variety of properties among millimetre-sized meteoroids proved different sources and histories of this material. Meteoroids that contain small grains tend to release their sodium early. For given grain sizes, the sodium in Na-poor meteoroids is released earlier than in meteors without sodium depletion. Overall, meteoroids with sodium depletion are revealed to have different structures: they have stronger material without very small grains and they do not show very bright wakes. Two iron meteoroids on Halley-type orbits were observed, thereby supporting the idea of large-scale mixing of material in the early solar system. The distribution of grain sizes of Jupiter-family members was in good agreement with results from the COSIMA instrument on the ROSETTA probe.
Context.
One of the most energetic bolide events in recent decades was detected by the US Government sensors (USGS) over remote areas of the Bering Sea on December 18, 2018, 23:48 UT. No ground-based ...optical observations exist.
Aims.
Using the satellite imagery of the dust trail left behind by the bolide, we tried to reconstruct the bolide trajectory. In combination with the bolide speed reported by the USGS, we computed the pre-atmospheric orbit. Observations in various spectral bands from 0.4 to 13.3
μ
m enabled us to study the dust properties.
Methods.
Images of the dust trail and its shadow obtained from various angles by the Multi-angle Imaging SpectroRadiometer (MISR) on board the Terra polar satellite and geostationary satellites Himawari-8 and Geostationary Operational Environmental Satellite 17 (GOES-17) were used. The initial position and orientation of the trail was varied, and its projections into the geoid coordinate grid were computed and compared with real data. Trail motion due to atmospheric wind was taken into account. Radiances and reflectances of selected parts of the dust trail were taken from the Moderate-resolution Imaging Spectroradiometer (MODIS) on board Terra. Reflectance spectra were compared with asteroid spectra.
Results.
The bolide radiant was found to be 13° ± 9° from that reported by the USGS, at azimuth 130° (from south to west) and zenith distance 14°. The bolide position was confirmed, including the height of maximum dust deposition around 25 km. The incoming asteroid had to be quite strong to maintain a high speed down to this height. The speed of 32 km s
−1
, reported by the USGS, was found to be plausible. The orbit had a high inclination of about 50° and a perihelion distance between 0.95–1 AU. The semimajor axis could not be restricted well but was most probably between 1–3 AU. The dust reflectance was much lower in the blue than in the red, consistent with the material of A- or L-type asteroid. The absorption at 11
μ
m confirms the presence of crystalline silicates in the dust.
ABSTRACT
The goal of this work is to determine if the dynamics of individual Taurid Complex (TC) objects are consistent with the formation of the complex via fragmentation of a larger body, or if the ...current orbital affinities between the TC members result from other dynamical processes. To this end, the orbital similarity through the time of comet 2P/Encke, 51 near-Earth asteroids (NEAs), and 16 Taurid fireballs was explored. Clones of each body were numerically simulated backwards in time, and epochs when significant fractions of the clones of any two bodies approached each other with both a low Minimum Orbit Intersection Distance and small relative velocity were identified. Only 12 pairs of bodies in our sample show such an association in the past 20 000 yr, primarily circa 3200 BCE. These include 2P/Encke and NEAs 2004 TG10, 2005 TF50, 2005 UR, 2015 TX24, and several Southern Taurid fireballs. We find this orbital convergence to be compatible with the fragmentation of a large parent body 5000–6000 yr ago, resulting in the separation of 2P/Encke and several NEAs associated with the TC, as well as some larger meteoroids now recorded in the Taurid stream. However, the influence of purely dynamical processes may offer an alternative explanation for this orbital rapprochement without requiring a common origin between these objects. In order to discriminate between these two hypotheses, future spectral surveys of the TC asteroids are required.
Aims.The observation of Draconid meteors was used to infer information on the structure, porosity, strength, and composition of the dust of comet 21P/Giacobini-Zinner. Methods.Stereoscopic video and ...photographic observations of six faint and one bright Draconid meteors provided meteor morphologies, heights, light curves, and atmospheric decelerations. The spectrum of the bright meteor was also obtained. We developed a simple model of meteoroid ablation and fragmentation. The model assumes that cometary meteoroids are composed of constituent grains. Results.By fitting the observed decelerations and light curves, we have found that the grain mass range was relatively narrow in all meteoroids but differed from case to case. Some meteoroids were coarse grained with grain masses 10-9 to 10-10 kg, others were fine grained with grain masses one order of magnitude lower. Individual mm-sized meteoroids contained tens of thousands to almost a million grains (assuming grain density close to 3000 kg m-3). The meteoroids were porous aggregates of grains, having porosities of about 90% and bulk densities of 300 kg m-3. Grain separation started after the surface of the meteoroid received energy of 106 J m-2. The separation continued during the first half of meteor trajectories. We call this phase erosion. The energy needed for grain erosion was 15-30$\times$ lower than the energy of vaporization. However, 30% of the largest meteoroid was resistant to thermal erosion; this part disrupted later mechanically under a very low dynamic pressure of 5 kPa. The relative abundances of Na, Mg, and Fe were nearly chondritic, but differential ablation caused preferential loss of sodium at the beginning of the trajectory.
ABSTRACT
The iron oxide ‘orange arc’ bands are unambiguously detected in persistent meteor trains, meteor wakes, and clouds, as well as in the terrestrial airglow. In contrast to the majority of ...other astronomically important diatomic molecules, theoretical simulation of the FeO rovibronic spectra is not feasible due to the extremely condensed and strongly perturbed multiplet structure of its excited states. In this work, the time-evolution of the laser-induced breakdown spectra (LIBS) of high-purity iron recorded in air at high temperature and impact conditions is used to mimic the FeO pseudo-continuum emission observed during meteor events and the terrestrial night airglow. The relative intensity distributions in the structural continuum of the LIBS spectra are measured at 530–660 nm and a plasma temperature of 1500–6500 K. The anomalous increase of the intensity observed at 620–640 nm and temperature < 2000 K could be attributed to the emission of higher oxides of iron as explained by the conducted thermodynamic and kinetic modelling of iron burning in the atmosphere.
Aims. We present a library of low-resolution meteor spectra that includes sporadic meteors, members of minor meteor showers, and major meteor showers. These meteors are in the magnitude range from +2 ...to −3, corresponding to meteoroid sizes from 1 mm to 10 mm. Methods. Parallel double-station video observations allowed us to compute heliocentric orbits for all meteors. Most observations were performed during the periods of activity of major meteor showers in the years between 2006 and 2012. Spectra are classified according to relative intensities of the low-temperature emission lines of Mg, Na, and Fe. Results. Shower meteors were found to be of normal composition, except for Southern δ Aquariids and some members of the Geminid shower, neither of which have Na in the meteor spectra. Variations in Na content are typical for the Geminid shower. Three populations of Na-free mereoroids were identified. The first population are iron meteorites, which have an asteroidal-chondritic origin, but one meteoroid with low perihelion (0.11 AU) was found among the iron meteorites. The second population were Sun-approaching meteoroids in which sodium is depleted by thermal desorption. The third population were Na-free meteoroids of cometary origin. Long exposure to cosmic rays on the surface of comets in the Oort cloud and disintegration of this crust might be the origin of this population of meteoroids.
Context.
A
τ
Herculid meteor outburst or even storm was predicted to occur by several models around 5 UT on 31 May 2022 as a consequence of the break-up of comet 73P/Schwassmann-Wachmann 3 in 1995. ...The multi-instrument and multi-station experiment was carried out within the Czech Republic to cover possible earlier activity of the shower between 21 and 1 UT on 30/31 May.
Aims.
We report meteor shower activity that occurred before the main peak and provide a comparison with the dynamical simulations of the stream evolution. The physical properties of the meteoroids are also studied.
Methods.
Multi-station observations using video and photographic cameras were used to calculate the atmospheric trajectories and heliocentric orbits of the meteors. Their arrival times were used to determine the shower activity profile. The physical properties of the meteoroids were evaluated using various criteria based on meteor heights. The evolution of the spectra of three meteors were studied as well.
Results.
This annual but poor meteor shower was active for the whole night many hours before the predicted peak. A comparison with dynamical models shows that a mix of older material ejected after 1900 and fresh particles originating from the 1995 comet fragmentation event was observed. The radiant positions of both groups of meteors were identified and were found to agree well with the simulated radiants. Meteoroids with masses between 10 mg and 10 kg were recorded. The mass distribution index was slightly higher than 2. The study of the physical properties shows that the
τ
Herculid meteoroids belong to the most fragile particles observed ever, especially among higher masses of meteoroids. The exceptionally bright bolide observed during the dawn represents a challenge for the dynamical simulations as it is necessary to explain how a half-metre body was transferred to the vicinity of the Earth at the same time as millimetre-sized particles.
A catalog of 824 fireballs (bright meteors), observed by a dedicated network of all-sky digital photographic cameras in central Europe in the years 2017–2018 is presented. The status of the European ...Fireball Network, established in 1963, is described. The cameras collect digital images of meteors brighter than an absolute magnitude of about −2 and radiometric light curves with a high temporal resolution of those brighter than a magnitude ≈−4. All meteoroids larger than 5 g, corresponding to sizes of about 2 cm, are detected regardless of their entry velocity. High-velocity meteoroids are detected down to masses of about 0.1 g. The largest observed meteoroid in the reported period 2017–2018 had a mass of about 100 kg and a size of about 40 cm. The methods of data analysis are explained and all catalog entries are described in detail. The provided data include the fireball date and time, atmospheric trajectory and velocity, the radiant in various coordinate systems, heliocentric orbital elements, maximum brightness, radiated energy, initial and terminal masses, maximum encountered dynamic pressure, physical classification, and possible shower membership. Basic information on the fireball spectrum is available for some bright fireballs (apparent magnitude <−7). A simple statistical evaluation of the whole sample is provided. The scientific analysis is presented in an accompanying paper.
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