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.
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.
Context. Several new meteor showers are added to the International Astronomical Union (IAU) list of meteor showers every year. Given the multiplication of video meteor measurements new parent bodies ...are to be found in addition to new showers. Such an endeavor is usually performed by comparing orbital elements, using a high threshold single-linking Dsh-criterion. However, questions remain about the accuracy of the method and the veracity of the newly associated parent bodies. Aims. Our goal is to find the presence of new parent bodies in a statistical meaningful way. Methods. A search for parent bodies was performed among SonotaCo and EDMOND databases. The association of asteroids with meteors was based on different methods, discussed and compared below. In addition, a thorough statistical test was performed in order to investigate the possible random associations. Results. A list of potential new parent bodies associated with at least 50 meteors is found. A statistical test was used to show whether the group of meteor orbits and the asteroid is a random coincidence or not. Out of 54 potential new parent bodies, only three new parent bodies are not excluded by the statistical test: 2014 BN14, 2015 TX24 and 2015 QT3, with a probability of chance occurrence of 37, 10 and 13%, respectively. This shows the need for rigorous method when searching for the existence of meteor showers and parent bodies. Conclusions. Ideally, such a test (or even better, tests) should be conducted in order to confirm (or not) the current IAU list of meteor showers. Similarly, all meteor orbit data in our databases should ideally be revisited using the latest methods providing a better estimate of the real uncertainty and accuracy of the derived orbits.
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.
The existence of pairs and groups of meteors during meteor showers has been an open question for a long time. The double-station video observation of the 2006 Geminid meteor shower, one of ...the most active annual showers, is used for the search of such events.
Aims.
The goal of the paper is to determine whether the observed pairs of Geminid meteors are real events or cases of random coincidence.
Methods.
The atmospheric trajectories of the observed meteors, photometric masses, and both time and spatial distances of meteoroids in the atmosphere were determined using a double-station video observation. The time gaps between them were analysed statistically. The Monte Carlo simulation was used for the determination of the probability of random pairings.
Results.
A higher than expected number of candidates for pairs was found among 2006 Geminids. An evaluation of the Poisson distribution shows that a significant fraction of them may be real cases. However, the Monte Carlo simulation did not confirm this result and provided a different view. Analysis of geometrical positions of candidate pairs also did not support the presence of real pairs and groups. Although we cannot exclude that some of them may be physically connected pairs, all the observed cases can be explained as the coincidental appearance of unrelated meteors.
Context. A bright fireball was observed above the Czech Republic on September 9, 2016, at 23:06:59 UT. Moreover, the video cameras at two different stations recorded eight fainter meteors flying on ...parallel atmospheric trajectories within less than 2 s. All the meteors belong to the September epsilon Perseid meteor shower. The measured proximity of all meteors during a very low activity meteor shower suggests that a cluster of meteors was observed. Aims. The goal of the paper is first to determine whether this event was a random occurrence or a real meteor cluster and second, if it was a cluster, to determine the epoch and at what distance from the Earth the separation of the particles occurred. Methods. The atmospheric trajectories of the observed meteors, masses, and relative distances of individual particles were determined using a double-station observation. According to the distances and masses of the particles, the most probable distance and time of fragmentation is determined. Results. The observed group of meteors is interpreted as the result of the orbital fragmentation of a bigger meteoroid. The fragmentation happened no earlier than 2 or 3 days before the encounter with the Earth at a distance smaller than ~0.08 AU from the Earth.
We present a survey of 97 spectra of mainly sporadic meteors in the magnitude range +3 to −1, corresponding to meteoroid sizes 1–10 mm. For the majority of the meteors, heliocentric orbits are known ...as well. We classified the spectra according to relative intensities of the lines of Mg, Na, and Fe. Theoretical intensities of these lines for a chondritic composition of the meteoroid and a wide range of excitation and ionization conditions were computed. We found that only a minority of the meteoroids show chondritic composition. Three distinct populations of Na-free meteoroids, each comprising ∼10% of sporadic meteoroids in the studied size range, were identified. The first population are meteoroids on asteroidal orbits containing only Fe lines in their spectra and possibly related to iron–nickel meteorites. The second population are meteoroids on orbits with small perihelia (
q
⩽
0.2
AU
), where Na was lost by thermal desorption. The third population of Na-free meteoroids resides on Halley type cometary orbits. This material was possibly formed by irradiation of cometary surfaces by cosmic rays in the Oort cloud. The composition of meteoroids on Halley type orbits is diverse, probably reflecting internal inhomogeneity of comets. On average, cometary dust has lower than chondritic Fe/Mg ratio. Surprisingly, iron meteoroids prevail among millimeter-sized meteoroids on typical Apollo-asteroid orbits. We have also found varying content of Na in the members of the Geminid meteoroid stream, suggesting that Geminid meteoroids were not released from their parent body at the same time.
Aims. The aim of the article is to show how the light curve of video-meteors can be described theoretically. Methods. The method of numerical integration of the system of differential equations ...describing the motion and ablation of a meteoroid during its atmospheric motion is employed. Results. We have shown that the modification of the ablation equation and the more general assumptions on the meteoroid cross-section behaviour can lead to a better description of light curves of faint video-meteors. The applied method indicates that the traditionally-used statistical parameter F could be replaced by another one, Levin's parameter μ, which has a physical meaning.
Double station data on 496 meteors belonging to several meteor showers were obtained within the program of the video meteor observations during years 1998-2001. Analyzed meteors cover a range of ...photometric masses from 10-7 to 10-4 kg with a corresponding range of maximum brightness from +4.7 to -2.1 absolute magnitude. Atmospheric trajectories of Perseid, Orionid and Leonid meteors are analysed. These typical cometary high velocity meteors are compared to Geminid meteors with probable asteroidal origin and Taurid meteors – another cometary shower with significantly lower entry velocity. The light curves of the studied meteors vary widely, but generally are nearly symmetrical with the point of maximum brightness located close the to middle of the luminous trajectory. Small differences between showers are reported. We found that the height data are in good agreement with the dust-ball model predictions. The only difference is the beginning height behaviour. The beginning heights of cometary meteors increase with increasing photometric mass. These meteoroids probably contain a volatile part which starts to ablate before we are able to detect the meteors. The Geminid meteors are a different case. They start to ablate suddenly and their beginning height is almost constant in the whole range of studied meteoroid masses. In this case we observe real beginnings of meteor ablation.
•Atmospheric and orbital data do not confirm existence of well defined meteor shower.•Similarity between the orbits is probably the result of chance coincidence.•Majority of the cloned orbits ...diverged from the orbit in a short time scale.•There are no faint meteors on the orbits of Příbram and Neuschwanstein meteorites.
The very next year following the fall of Neuschwanstein meteorites and discovery of their orbital similarity with the Příbram meteorite, dedicated observational campaigns aiming for the detection of faint meteors on similar orbits were started. The goal of this paper is to process all the data collected within 7years, to analyze their atmospheric trajectories and heliocentric orbits and to investigate the possibility that they belong to the stream.
The trajectories and orbits of the detected meteors were used to determine whether those meteors are members of the same shower. An orbital evolution model was applied on a certain number of cloned particles to investigate their possible connection with the meteorite stream. Statistical tests were conducted to determine if such small sample of the orbits is similar by chance or if the stream is real. It was found that from the observational as well as the theoretical point of view it is impossible to prove the existence of faint meteor shower connected with the Příbram and Neuschwanstein meteorite stream.
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