Vlastnosti slabých meteorů studovaných pomocí videotechniky

Dvoustaniční a spektrální video pozorování meteorů jsou přínosnem pro studium mili- metrových meteoroidů. Takřka dvě desítky let video pozorování z Ondřejovské observatoře nabízí rozsáhlou databázi těchto pozorování. V této práci kombinujeme výsledky studia spekter malých meteorů s výsledky z modelu fragmentace malých meteoroidů. Spolu s úplnou informací o trajektorii a oběžné dráze meteoroidu můžeme lépe porozumět původu a vnitřní struktuře milimetrových těles. Zjistili jsme, že vypařování sodíku z meteoroidu zavisí na velikosti zrn z kterých se meteoroidy skládají. Tělesa s menšími zrny mají tendeci vyzářit sodík dříve než ostatní prvky. Tělesa s nižším obsahem sodíku se obecně odlišovala od jiných spektrálních tříd. Pro danou velikost zrn vyzářily sodík dříve, měly spíše větší pevnost a menší hmotnost a tvořily spíše slabší wake (či žádný). Dva železné meteoroidy na drahách podobných kometám Halleyova typu jsou zřejmě důkazem složitého vývoje mladé Slunenčí soustavy. Rozdělení velikostí zrn meteoroidů na drahách podobných kometám Jupiterovy rodiny bylo ve shodě s výsledky z přístroje COSIMA na sondě ROSETTA, která zkoumala kometu 67P/Churyumov-Gerasimenko.Parallel double-station video observations paired with spectroscopic video observations are a good way to study millimetre-sized meteoroids. Almost two decades of video observations of meteors at the Ondřejov observatory give us broad database to study large quantities of meteoroids and their properties. In this work we combined spectral video observations and results of the modelling of the fragmentation of meteoroids. Along with complex infor- mation about meteoroid's trajectories and orbits, this can give us better understanding about origin, internal structure etc. of these millimetre-sized interplanetary bodies. Meteoroids that contained small grains tend to release the sodium early. Since there is a smaller amount of sodium for Na depleted meteoroids, the sodium was released earlier than it was released for meteoroids with same grain sizes and without the sodium depletion. Overall, meteoroids with sodium depletion showed different composition: they were composed of stronger material without very small grains and they did not showed very bright wakes. Two iron meteoroids on Halley type orbits were observed. They are probably remnants of complicated early years of our solar system. The dis- tribution of grain sizes of Jupiter-family members was in a good agreements with results from the COSIMA...Matematicko-fyzikální fakultaFaculty of Mathematics and Physic

Properties of the Orionid meteors observed in 2006

In the present work we study the Orionid 2006 meteor shower. All results in this work come from double station video observations. We study exceptional activity, caused most probably by particles trapped in resonance motion with Jupiter. We focused on light curves, atmospheric trajectories and orbital elements of meteoroids. We can find here comparison with other years of activity of the Orionid meteor shower and comparison with other annual meteor showers

Properties of faint meteors studied by video observations

Parallel double-station video observations paired with spectroscopic video observations are a good way to study millimetre-sized meteoroids. Almost two decades of video observations of meteors at the Ondřejov observatory give us broad database to study large quantities of meteoroids and their properties. In this work we combined spectral video observations and results of the modelling of the fragmentation of meteoroids. Along with complex infor- mation about meteoroid's trajectories and orbits, this can give us better understanding about origin, internal structure etc. of these millimetre-sized interplanetary bodies. Meteoroids that contained small grains tend to release the sodium early. Since there is a smaller amount of sodium for Na depleted meteoroids, the sodium was released earlier than it was released for meteoroids with same grain sizes and without the sodium depletion. Overall, meteoroids with sodium depletion showed different composition: they were composed of stronger material without very small grains and they did not showed very bright wakes. Two iron meteoroids on Halley type orbits were observed. They are probably remnants of complicated early years of our solar system. The dis- tribution of grain sizes of Jupiter-family members was in a good agreements with results from the COSIMA..

Properties of faint meteors studied by video observations

Parallel double-station video observations paired with spectroscopic video observations are a good way to study millimetre-sized meteoroids. Almost two decades of video observations of meteors at the Ondřejov observatory give us broad database to study large quantities of meteoroids and their properties. In this work we combined spectral video observations and results of the modelling of the fragmentation of meteoroids. Along with complex infor- mation about meteoroid's trajectories and orbits, this can give us better understanding about origin, internal structure etc. of these millimetre-sized interplanetary bodies. Meteoroids that contained small grains tend to release the sodium early. Since there is a smaller amount of sodium for Na depleted meteoroids, the sodium was released earlier than it was released for meteoroids with same grain sizes and without the sodium depletion. Overall, meteoroids with sodium depletion showed different composition: they were composed of stronger material without very small grains and they did not showed very bright wakes. Two iron meteoroids on Halley type orbits were observed. They are probably remnants of complicated early years of our solar system. The dis- tribution of grain sizes of Jupiter-family members was in a good agreements with results from the COSIMA..

Asteroids in an excited state of rotation

Astronomický ústav UKAstronomical Institute of Charles UniversityFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Bright Perseid fireball with exceptional beginning height of 170 km observed by different techniques

We report multi-instrumental observation of a bright fireball belonging to the Perseid meteor shower, which was recorded simultaneously by 11 all-sky photographic cameras, one high-resolution 300 mm photographic camera, two digital all-sky cameras, one wide-field digital camera, and two analog image-intensified video cameras on 12 August in 2012 at 22:29:46 UT. An exceptional beginning height of 170 km makes this fireball the highest Perseid ever observed and the highest meteor ever observed with precise atmospheric trajectory and heliocentric orbit not belonging to the Leonid shower. Moreover, one spectral video camera recorded the spectrum of the fireball. The spectrum shows only atmospheric emissions of O, N, and N2 above 130 km. Below 110 km, the spectrum is not markedly different from other Perseid fireballs. The spectrum of the persistent train was also recorded, and a double-station observation of the persistent train provided its vertical and horizontal motion

Small iron meteoroids

Context. A significant fraction of small meteors are produced by iron meteoroids. Their origin and the interaction with the atmosphere have not been well explained up to now. Aims. The goals of the study are to observe faint, slow, low altitude meteors, to identify candidates for iron meteoroids among them, to model their ablation and light curves, and to determine their properties. Methods. Double station video observations were used for the determination of atmospheric trajectories, heliocentric orbits, light curves, and spectra of meteors. Meteors with iron spectra or of suspected iron composition based on beginning heights and light curves were modeled. The immediate removal of liquid iron from the surface as a cloud of droplets with Nukiyama–Tanasawa size distribution and their subsequent vaporization was assumed as the main ablation process on the basis of our previous work. The numerical model has only five parameters: meteoroid initial velocity v∞, zenith distance z, initial mass m∞, mean drop size Ddr, and luminous efficiency τ. The theoretical light curves were compared with the observed ones. Results. The model is able to explain the majority of the selected light curves, and meteoroid parameters that are not directly observable – m∞, Ddr, and τ – are determined. Unlike in most meteor studies, the mass and luminous efficiency are determined independently. Luminous efficiency ranges from 0.08 to 5.8%; it weakly decreases with increasing initial meteoroid mass. No simple dependency on initial velocity was found. The mean size of iron drops depends on the meteoroid velocity. Slower meteoroids can produce drops with a wide range of mean sizes, whereas faster ones are better matched with larger drops with a smaller dispersion of sizes

Properties of Alpha Monocerotid meteors from the observation of the 2019 outburst in the Czech Republic

We observed the predicted outburst of the Alpha Monocerotid (AMO) meteor shower on 2019 November 22 with our modernized video and photographic cameras. Due to the short duration and moderate intensity of the outburst, atmospheric trajectories and radiants were obtained for only ten meteors, seven of which included velocities, magnitudes, and orbits. In addition, one incomplete video spectrum was captured. The radiants and orbits were found to be compatible with that of the 1995 outburst. The spectrum confirmed that AMO meteoroids are deficient in sodium. Unlike any other meteor shower, meteor end heights were found to be distributed along a constant level of 90 km for all meteors with magnitudes between +4 and −2 and with atmospheric trajectory lengths up to 40 km. We propose that Alpha Monocerotids were formed from a devolatilized and fragile cometary crust composed from relatively large fundamental grains