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1.
The orbit of the Chelyabinsk object is calculated, applying the least‐squares method directly to astrometric positions. The dynamical evolution of this object in the past is studied by integrating equations of motion for particles with orbits from the confidence region. It is found that the majority of the Chelyabinsk clones reach the near‐Sun state. Sixty‐seven percent of these objects have collisions with the Sun for 15 Myr in our numerical simulations. The distribution of minimum solar distances shows that the most probable time for the encounters of the Chelyabinsk object with the Sun lies in the interval from ?0.8 Myr to ?2 Myr. This is consistent with the estimate of a cosmic ray exposure age of 1.2 Myr (Popova et al. 2013). A parent body of the Chelyabinsk object should experience strong tidal and thermal effects at this time. The possible association of the Chelyabinsk object with 86039 (1999 NC43) and 2008 DJ is discussed.  相似文献   

2.
The entry and subsequent breakup of the ~17–20 m diameter Chelyabinsk meteoroid deposited approximately 500 kT of TNT equivalent energy to the atmosphere, causing extensive damage that underscored the hazard from small asteroid impacts. The breakup of the meteoroid was characterized by intense fragmentation that dispersed most of the original mass. In models of the entry process, the apparent mechanical strength of the meteoroid during fragmentation, ~1–5 MPa, is two orders of magnitude lower than the mechanical strength of the surviving meteorites, ~330 MPa. We implement a two-material computer code that allows us to fully simulate the exchange of energy and momentum between the entering meteoroid and the interacting atmospheric air. Our simulations reveal a previously unrecognized process in which the penetration of high-pressure air into the body of the meteoroid greatly enhances the deformation and facilitates the breakup of meteoroids similar to the size of Chelyabinsk. We discuss the mechanism of air penetration that accounts for the bulk fragmentation of an entering meteoroid under conditions similar to those at Chelyabinsk, to explain the surprisingly low values of the apparent strength of the meteoroid during breakup.  相似文献   

3.
The work presents modern ideas on the physical mechanism of explosion of large meteoroids (superbolides) in the Earth’s atmosphere at the end of their trajectories. As a result of our work, the values of following parameters were obtained: the altitude of the beginning of the aerodynamic destruction of a meteoroid like the Chelyabinsk superbolide; the altitude of a relatively very thin layer, characterized by sharp aerodynamic deceleration of a fragmenting and laterally expanding space object, accompanied by an impulse transformation of kinetic energy into thermal energy with plasma generation which results in intense electromagnetic radiation and an explosive shock wave; and, the initial temperature of such a plasma.  相似文献   

4.
Data received from a network of ionosondes located at distances of 1500–3100 km from the Chelyabinsk meteorite site are used to analyze ionospheric disturbances at a height of approximately 300 km following the flight and explosion of the space body. The fall of the meteoroid is believed to be accompanied by the generation of gravitational waves in the neutral atmosphere and traveling ionospheric disturbances. The velocity and period of the latter are 600–700 m/s and 70–135 min, respectively; the amplitude of relative electron concentration disturbances is 10–20%. There is evidence of the 6–7 h ionospheric presence of wave electron concentration disturbances with relative amplitude of 10–20%, which could have been caused by long-living whirlwinds in the upper atmosphere.  相似文献   

5.
On February 15, 2013, after the observation of a brilliant fireball and a spectacular airburst over the southern Ural region (Russia), thousands of stones fell and were rapidly recovered, bringing some extremely fresh material for scientific investigations. We undertook a multidisciplinary study of a dozen stones of the Chelyabinsk meteorite, including petrographic and microprobe investigations to unravel intrinsic characteristics of this meteorite. We also study the short and long‐lived cosmogenic radionuclides to characterize the initial meteoroid size and exposure age. Petrographic observations, as well as the mineral compositions obtained by electron microprobe analyses, allow us to confirm the classification of the Chelyabinsk meteorite as an LL5 chondrite. The fragments studied, a few of which are impact melt rocks, contain abundant shock melt veins and melt pockets. It is likely that the catastrophic explosion and fragmentation of the Chelyabinsk meteoroid into thousands of stones was in part determined by the initial state of the meteoroid. The radionuclide results obtained show a wide range of concentrations of 14C, 22Na, 26Al, 54Mn, 57Co, 58Co, and 60Co, which indicate that the pre‐atmospheric object had a radius >5 m, consistent with other size estimates based on the magnitude of the airburst caused by the atmospheric entry and breakup of the Chelyabinsk meteoroid. Considering the observed 26Al activities of the investigated samples, Monte Carlo simulations, and taking into account the 26Al half‐life (0.717 Myr), the cosmic‐ray exposure age of the Chelyabinsk meteorite is estimated to be 1.2 ± 0.2 Myr. In contrast to the other radionuclides, 14C showed a very large range only consistent with most samples having been exposed to anthropogenic sources of 14C, which we associate with radioactive contamination of the Chelyabinsk region by past nuclear accidents and waste disposal, which has also been confirmed by elevated levels of anthropogenic 137Cs and primordial 40K in some of the Chelyabinsk fragments.  相似文献   

6.
Numerical simulation of atmospheric disturbances during the first hours after the Chelyabinsk and Tunguska space body impacts has been carried out. The results of detailed calculations, including the stages of destruction, evaporation and deceleration of the cosmic body, the generation of atmospheric disturbances and their propagation over distances of thousands of kilometers, have been compared with the results of spherical explosions with energy equal to the kinetic energy of meteoroids. It has been shown that in the case of the Chelyabinsk meteorite, an explosive analogy provides acceptable dimensions of the perturbed region and the perturbation amplitude. With a more powerful Tunguska fall, the resulting atmospheric flow is very different from the explosive one; an atmospheric plume emerges that releases matter from the meteoric trace to an altitude of the order of a thousand kilometers.  相似文献   

7.

The LP/OMPS limb sensor of the Suomi satellite detected the atmospheric trace of the Chelyabinsk superbolide with an energy of over 400 kt TNT in 2013. The study of LP/OMPS data shows that it detects several bolides with much less energy each year. The paper considers the cases of observation of three bolides in 2016–2017: on February 6, 2016 (13 kt), March 3, 2016 (0.19 kt), and March 9, 2017 (1 kt). The possibility of improving the detection of bolides using a limb sensor in the form of a microsatellite with an increased number of observation regions along the horizon is discussed. Several such microsatellites will be able to track most of the bodies larger than a meter that burn up in the atmosphere of the Earth or Mars.

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8.
The atmospheric detonation of a 17 m-asteroid above Chelyabinsk, Russia on 2013 February 15 shows that even small asteroids can cause extensive damage. Earth-based telescopes have found smaller harmless objects, such as 2008 TC3, a 4 m-asteroid that was discovered 20h before it exploded over northeastern Sudan (Jenniskens, 2009). 2008 TC3 remains the only asteroid discovered before it hit Earth because it approached Earth from the night side, where it was observed by large telescopes searching for near-Earth objects (NEO’s). The larger object that exploded over Chelyabinsk approached Earth from the day side, from too close to the Sun to be detected from Earth. A sizeable telescope in an orbit about the Sun-Earth L1 (SE-L1) libration point could find objects like the “Chelyabinsk” asteroid approaching approximately from the line of sight to the Sun about a day before Earth closest approach. Such a system would have the astrometric accuracy needed to determine the time and impact zone for a NEO on a collision course. This would give at least several hours, and usually 2–4 days, to take protective measures, rather than the approximately two-minute interval between the flash and shock wave arrival that occurred in Chelyabinsk. A perhaps even more important reason for providing warning of these events, even smaller harmless ones that explode high in the atmosphere with the force of an atomic bomb, is to prevent mistaking such an event for a nuclear attack that could trigger a devastating nuclear war. A concept using a space telescope similar to that needed for an SE-L1 monitoring satellite, is already conceived by the B612 Foundation, whose planned Sentinel Space Telescope could find nearly all 140 m and larger NEO’s, including those in orbits mostly inside the Earth’s orbit that are hard to find with Earth-based telescopes, from a Venus-like orbit (Lu, 2013). Few modifications would be needed to the Sentinel Space Telescope to operate in a SE-L1 orbit, 0.01 AU from Earth towards the Sun, to find most asteroids larger than about 5 meters that approach the Earth from the solar direction. The spacecraft would scan 165 square degrees of the sky around the Earth every hour, finding asteroids when they are brightest (small phase angle) as they approach Earth. We will undertake Monte Carlo studies to see what fraction of asteroids 5 m and larger approaching from the Sun might be found by such a mission, and how much warning time might typically be expected. Also, we will check the overall coverage for all Earth-approaching NEO’s, including ground-based observations and observations by the recently-launched NEOSSat, which may best fill any gaps in coverage between that provided by an SE-L1 telescope and ground-based surveys. Many of the objects as large as 50 m, like the one that created Meteor Crater in Arizona, will not be found by current NEO surveys, while they would usually be seen by this possible mission even if they approached from the direction of the Sun. We should give better warning for future “Bolts out of the blue.”  相似文献   

9.
Simultaneous, also called electrophonic sounds were widely reported by eye-witnesses to the Chelyabinsk fireball. The available data indicate that such sounds were heard at ranges to at least ~100 km from the fireball’s atmospheric path. We estimate that the fireball may have generated of order 625 W of energy in the form of very low frequency radiation, and we find some tentative evidence to indicate that the acoustic conversion efficiency at a 100 km range was of order 0.1 %. Numerical simulations of the atmospheric flight path indicate that electrophonic sounds should have commenced some 5 s after the fireball first became luminous and would have lasted for some 7.5 s prior to the moment of catastrophic break-up.  相似文献   

10.
Asteroids and comets 10–100 m in size that collide with Earth disrupt dramatically in the atmosphere with an explosive transfer of energy, caused by extreme air drag. Such airbursts produce a strong blastwave that radiates from the meteoroid's trajectory and can cause damage on the surface. An established technique for predicting airburst blastwave damage is to treat the airburst as a static source of energy and to extrapolate empirical results of nuclear explosion tests using an energy‐based scaling approach. Here we compare this approach to two more complex models using the iSALE shock physics code. We consider a moving‐source airburst model where the meteoroid's energy is partitioned as two‐thirds internal energy and one‐third kinetic energy at the burst altitude, and a model in which energy is deposited into the atmosphere along the meteoroid's trajectory based on the pancake model of meteoroid disruption. To justify use of the pancake model, we show that it provides a good fit to the inferred energy release of the 2013 Chelyabinsk fireball. Predicted overpressures from all three models are broadly consistent at radial distances from ground zero that exceed three times the burst height. At smaller radial distances, the moving‐source model predicts overpressures two times greater than the static‐source model, whereas the cylindrical line‐source model based on the pancake model predicts overpressures two times lower than the static‐source model. Given other uncertainties associated with airblast damage predictions, the static‐source approach provides an adequate approximation of the azimuthally averaged airblast for probabilistic hazard assessment.  相似文献   

11.
We consider the very-high-energy (VHE) gamma-ray observations of the blazar 1ES 2344+514 in 2003 in comparison with the data of its ASM/RXTE X-ray monitoring. A VHE gamma-ray flux was detected from the observed object at a confidence level of ≈ 5σ and it was estimated to be 1.85 ± 0.68 Crab (E ≥ 1 TeV). The observations revealed a VHE gamma-ray burst from the object that occurred in September 2003 and that lasted for no more than 4 days. The burst was also confirmed in the X-ray (2–12 keV) energy range. Analysis of the observational data showed evidence of a correlation between the fluxes in the two energy ranges and invoking the previous observations of 1ES 2344+514 in 2002 allowed this correlation to be refined in a wide range of fluxes.  相似文献   

12.
We studied three lithologies (light and dark chondritic and impact melt rock) differing in shock stage from the LL5 chondrite Chelyabinsk. Using the 40Ar-39Ar dating technique, we identified low- and high-temperature reservoirs within all samples, ascribed to K-bearing oligoclase feldspar and shock-induced jadeite–feldspar glass assemblages in melt veins, respectively. Trapped argon components had variable 40Ar/36Ar ratios even within low- and high-temperature reservoirs of individual samples. Correcting for trapped argon revealed a lithology-specific response of the K-Ar system to shock metamorphism, thereby defining two distinct impact events affecting the Chelyabinsk parent asteroid (1) an intense impact event ~1.7 ± 0.1 Ga ago formed the light–dark-structured and impact-veined Chelyabinsk breccia. Such a one-stage breccia formation is consistent with petrological observations and was recorded by the strongly shocked lithologies (dark and impact melt) where a significant fraction of oligoclase feldspar was transformed into jadeite and feldspathic glass; and (2) a young reset event ~30 Ma ago particularly affected the light lithology due to its low argon retentivity, while the more retentive shock-induced phases were more resistant against thermal reset. Trapped argon with 40Ar/36Ar ratios up to 1900 was likely incorporated during impact-induced events on the parent body, and mixed with terrestrial atmospheric argon contamination. Had it not been identified via isochrons based on high-resolution argon extraction, several geochronologically meaningless ages would have been deduced.  相似文献   

13.
Long TeV γ-ray campaigns have been carried out to study the spectrum, variability and duty cycle of the BL Lac object Markarian 421. These campaigns have given some evidence of the presence of protons in the jet: (i) Its spectral energy distribution which shows two main peaks; one at low energies (∼1 keV) and the other at high energies (hundreds of GeV), has been described by using synchrotron proton blazar model. (ii) The study of the variability at GeV γ-rays and X-rays has indicated no significant correlation. (iii) TeV γ-ray detections without activity in X-rays, called “orphan flares” have been observed in this object.Recently, The Telescope Array Collaboration reported the arrival of 72 ultra-high-energy cosmic rays with some of them possibly related to the direction of Markarian 421. The IceCube Collaboration reported the detection of 37 extraterrestrial neutrinos in the TeV–PeV energy range collected during three consecutive years. In particular, no neutrino track events were associated with this source. In this paper, we consider the proton–photon interactions to correlate the TeV γ-ray fluxes reported by long campaigns with the neutrino and ultra-high-energy cosmic ray observations around this blazar. Considering the results reported by The IceCube and Telescope Array Collaborations, we found that only from ∼25% to 70% of TeV fluxes described with a power law function with exponential cutoff can come from the proton–photon interactions.  相似文献   

14.
When cosmic bodies of asteroidal and cometary origin, with a size from 20 to approximately 100 m, enter dense atmospheric layers, they are destroyed with a large probability under the action of aerodynamic forces and decelerated with the transfer of their energy to the air at heights from 20–30 to several kilometers. The forming shock wave reaches the Earth’s surface and can cause considerable damage at great distances from the entry path similar to the action of a high-altitude explosion. We have performed a numerical simulation of the disruption (with allowance for evaporation of fragments) and deceleration of meteoroids having the aforesaid dimensions and entering the Earth’s atmosphere at different angles and determined the height of the equivalent explosion point generating the same shock wave as the fall of a cosmic body with the given parameters. It turns out that this height does not depend on the velocity of the body and is approximately equal to the height at which this velocity is reduced by half. The obtained results were successfully approximated by a simple analytical formula allowing one to easily determine the height of an equivalent explosion depending on the dimensions of the body, its density, and angle of entry into the atmosphere. A comparison of the obtained results with well-known approximate analytical (pancake) models is presented and an application of the obtained formula to specific events, in particular, to the fall of the Chelyabinsk meteorite on February 15, 2013, and Tunguska event of 1908, is discussed.  相似文献   

15.
Three masses of the Chelyabinsk meteorite have been studied with a wide range of analytical techniques to understand the mineralogical variation and thermal history of the Chelyabinsk parent body. The samples exhibit little to no postentry oxidation via Mössbauer and Raman spectroscopy indicating their fresh character, but despite the rapid collection and care of handling some low levels of terrestrial contamination did nonetheless result. Detailed studies show three distinct lithologies, indicative of a genomict breccia. A light‐colored lithology is LL5 material that has experienced thermal metamorphism and subsequent shock at levels near S4. The second lithology is a shock‐darkened LL5 material in which the darkening is caused by melt and metal‐troilite veins along grain boundaries. The third lithology is an impact melt breccia that formed at high temperatures (~1600 °C), and it experienced rapid cooling and degassing of S2 gas. Portions of light and dark lithologies from Chel‐101, and the impact melt breccias (Chel‐102 and Chel‐103) were prepared and analyzed for Rb‐Sr, Sm‐Nd, and Ar‐Ar dating. When combined with results from other studies and chronometers, at least eight impact events (e.g., ~4.53 Ga, ~4.45 Ga, ~3.73 Ga, ~2.81 Ga, ~1.46 Ga, ~852 Ma, ~312 Ma, and ~27 Ma) are clearly identified for Chelyabinsk, indicating a complex history of impacts and heating events. Finally, noble gases yield young cosmic ray exposure ages, near 1 Ma. These young ages, together with the absence of measurable cosmogenic derived Sm and Cr, indicate that Chelyabinsk may have been derived from a recent breakup event on an NEO of LL chondrite composition.  相似文献   

16.
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17.
We have empirically estimated how often fireball shocks produce overpressure (∆P) at the ground sufficient to damage windows. Our study used a numerical entry model to estimate the energy deposition and shock production for a suite of 23 energetic fireballs reported by U.S. Government sensors over the last quarter century. For each of these events, we estimated the peak ∆P on the ground and the ground area above ∆P thresholds of 200 and 500 Pa where light and heavy window damage, respectively, are expected. Our results suggest that at the highest ∆P, it is the rare, large fireballs (such as the Chelyabinsk fireball) which dominate the long-term areal ground footprints for heavy window damage. The height at the fireball peak brightness and the fireball entry angle contribute to the variance in ground ∆P, with lower heights and shallower angles producing larger ground footprints and more potential damage. The effective threshold energy for fireballs to produce heavy window damage is ~5–10 kT; such fireballs occur globally once every 1–2 years. These largest annual bolide events, should they occur over a major urban center with large numbers of windows, can be expected to produce economically significant window damage. However, the mean frequency of heavy window damage (∆P above 500 Pa) from fireball shock waves occurring over urban areas is estimated to be approximately once every 5000 yr. Light window damage (∆P above 200 Pa) is expected every ~600 yr.  相似文献   

18.
The observational evidence for infall associated with star formation is discussed. Whilst spectral energy distributions of young protostellar objects are consistent with infall, the best direct evidence comes from millimetre and sub-millimetre spectral line observations. Considerations of the formation of the line profiles and the chemical effects of gas-grain interactions suggest that there is only a very short ‘window’ in the evolutionary track of a protostellar object during which infall is directly observable. This may explain why so few infall candidates have been detected. It is argued that self-consistent models of the dynamical and chemical evolution of collapsing cores, coupled to multiple high resolution line observations, will provide definitive evidence for the presence of infall in these objects.  相似文献   

19.
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X‐ray map of a thin section of a sample of the Chelyabinsk meteorite from the study of Righter et al. (pp. 1790–1819). Sample Chel‐102 contains roughly 50 modal% of a dark lithology that is shock‐darkened LL5 chondrite (left side of image). There is heavy veining of this portion, and very little original equilibrated chondritic texture remaining. The other 50% of Chel‐102 (right side of image) is a very fi ne‐grained melt breccia comprised of mesostasis (85%), metal‐troilite droplets (5%), and chondritic fragments of similar mineralogy to the light lithology of Chel‐101. Image produced by Eve. L. Berger.  相似文献   

20.
It is suggested that a collapsing supermassive object, which acts as an ultra-high energy particle accelerator, is the precursor of an active galactic nucleus and that the gravitational energy released during the collapse of the object is locked in the quark-gluon plasma permeated by leptons into which the entire matter in the core of the object is converted as a result of the collapse. It is also pointed out that the collapse of the object to a space-time singularity is inhibited by Pauli's exclusion principle as well as by Heisenberg's uncertainty principle and that the object explodes, before it could collapse to a singularity, thereby releasing the enormous amount of energy locked in the quark-gluon plasma.  相似文献   

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