The Experts below are selected from a list of 21 Experts worldwide ranked by ideXlab platform
David Capek - One of the best experts on this subject based on the ideXlab platform.
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Rotation of Cometary meteoroids
Astronomy & Astrophysics, 2014Co-Authors: David CapekAbstract:Aims. The rotation of meteoroids caused by gas drag during the ejection from a Cometary nucleus has not been studied yet. The aim of this study is to estimate the rotational characteristics of meteoroids after their release from a Comet during normal activity. Methods. The basic dependence of spin rate on ejection velocity and meteoroid size is determined analytically. A sophisticated numerical model is then applied to meteoroids ejected from the 2P/Encke Comet. The meteoroid shapes are approximated by polyhedrons, which have been determined by a 3D laser scanning method of 36 terrestrial rock samples. These samples come from three distinct sets with different origins and characteristics, such as surface roughness or angularity. Two types of gas-meteoroid interactions and three gas ejection models are assumed. The rotational characteristics of ejected meteoroid population are obtained by numerical integration of equations of motion with random initial conditions and random shape selection. Results. It is proved that the results do not depend on a specific set of shape models and that they are applicable to the (unknown) shapes of real meteoroids. A simple relationship between the median of meteoroid spin frequencies f (Hz), ejection velocities vej (m s−1), and sizes D (m) is determined. For diffuse reflection of gas molecules from meteoroid’s surface it reads as f 2×10−3vejD−0.88, and for specular reflection of gas molecules from meteoroid’s surface it is f 5 × 10−3vejD−0.88. The distribution of spin frequencies is roughly normal on log scale, and it is relatively wide: a 2σ-interval can be described as (0.1, 10) × f . Most of the meteoroids are non-principal axis rotators. The median angle between angular momentum vector and spin vector is 12◦. About 60% of meteoroids rotate in long-axis mode. The distribution of angular momentum vectors is not random. They are concentrated in the perpendicular direction with respect to the gas flow direction. These results have been determined for the 2P/Encke Comet, but their validity is general.
Dina Capek - One of the best experts on this subject based on the ideXlab platform.
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Rotation of Cometary meteoroids
Astronomy and Astrophysics, 2014Co-Authors: Dina CapekAbstract:The aim of this study is to estimate the rotational characteristics of meteoroids after their release from a Comet during normal activity. The results can serve as initial conditions for further analyses of subsequent evolution of rotation in the interplanetary space. A sophisticated numerical model was applied to meteoroids ejected from 2P/Encke Comet. The meteoroid shapes were approximated by polyhedrons with several thousands of surface elements, which have been determined by 3D laser scanning method of 36 terrestrial rock samples. These samples came from three distinct sets with different origin and shape characteristics. Two types of gas-meteoroid interactions (diffuse and specular reflection of gas molecules from the surface of meteoroid) and three gas ejection models (leading to very different ejection velocities) were assumed. The rotational characteristics of ejected meteoroid population were obtained by numerical integration of equations of motion with random initial conditions and random shape selection. It was proved, that the results do not depend on specific set of shape models and that they are applicable to (unknown) shapes of real meteoroids. A simple relationship between median of meteoroid spin frequencies $\bar{f}$ (Hz), ejection velocities $v_{\rm ej}$ (m s$^{-1}$) and sizes $D$ (m) was determined. For diffuse reflection of gas molecules from meteoroid's surface it is: $\bar{f}\simeq 2\times 10^{-3} v_{\rm ej} D^{-0.88}$, and for specular reflection of gas molecules from meteoroid's surface it is: $\bar{f}\simeq 5\times 10^{-3} v_{\rm ej} D^{-0.88}$. The distribution of spin frequencies is relatively wide; $2\sigma$-interval can be described as $\sim(0.1, 10)\times \bar{f}$. The results were determined for 2P/Encke Comet, but it was shown that their validity is general.
Vincenzo Orofino - One of the best experts on this subject based on the ideXlab platform.
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Taurid Complex Smoking Gun: Detection of Cometary Activity
arXiv: Earth and Planetary Astrophysics, 2020Co-Authors: Ignacio Ferrin, Vincenzo OrofinoAbstract:Using the Secular Light Curve (SLC) formalism (Ferr\'in, 2010), we have catalogued 88 probable members of the Taurid Complex (TC). 51 of them have useful SLCs and 34 of these (67%) exhibit Cometary activity. This high percentage of active asteroids gives support to the hypothesis of a catastrophe that took place during the Upper Paleolithic (Clube and Napier, 1984), when a large short-period Comet, arriving in the inner Solar System from the Kuiper Belt, experienced, starting from 20 thousand years ago, a series of fragmentations that produced the present 2P/Encke Comet, together with a large number of other members of the TC. The fragmentation of the progenitor body was facilitated by its heterogeneous structure (very similar to a rubble pile) and this also explains the current coexistence in the complex of fragments of different composition and origin. We have found that (2212) Hephaistos and 169P/NEAT are active and members of the TC with their own sub-group. Other components of the complex are groups of meteoroids, that often give rise to meteor showers when they enter the terrestrial atmosphere, and very probably also the two small asteroids that in 1908 and 2013 exploded in the terrestrial atmosphere over Tunguska and Chelyabinsk, respectively. What we see today of the TC are the remnants of a very varied and numerous complex of objects, characterized by an intense past of collisions with the Earth which may continue to represent a danger for our planet.
Orofino Vincenzo - One of the best experts on this subject based on the ideXlab platform.
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Taurid Complex Smoking Gun: Detection of Cometary Activity
2020Co-Authors: Ferrin Ignacio, Orofino VincenzoAbstract:Using the Secular Light Curve (SLC) formalism (Ferr\'in, 2010), we have catalogued 88 probable members of the Taurid Complex (TC). 51 of them have useful SLCs and 34 of these (67%) exhibit Cometary activity. This high percentage of active asteroids gives support to the hypothesis of a catastrophe that took place during the Upper Paleolithic (Clube and Napier, 1984), when a large short-period Comet, arriving in the inner Solar System from the Kuiper Belt, experienced, starting from 20 thousand years ago, a series of fragmentations that produced the present 2P/Encke Comet, together with a large number of other members of the TC. The fragmentation of the progenitor body was facilitated by its heterogeneous structure (very similar to a rubble pile) and this also explains the current coexistence in the complex of fragments of different composition and origin. We have found that (2212) Hephaistos and 169P/NEAT are active and members of the TC with their own sub-group. Other components of the complex are groups of meteoroids, that often give rise to meteor showers when they enter the terrestrial atmosphere, and very probably also the two small asteroids that in 1908 and 2013 exploded in the terrestrial atmosphere over Tunguska and Chelyabinsk, respectively. What we see today of the TC are the remnants of a very varied and numerous complex of objects, characterized by an intense past of collisions with the Earth which may continue to represent a danger for our planet.Comment: 45 pages, 16 Figures, 9 Table
Ignacio Ferrin - One of the best experts on this subject based on the ideXlab platform.
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Taurid Complex Smoking Gun: Detection of Cometary Activity
arXiv: Earth and Planetary Astrophysics, 2020Co-Authors: Ignacio Ferrin, Vincenzo OrofinoAbstract:Using the Secular Light Curve (SLC) formalism (Ferr\'in, 2010), we have catalogued 88 probable members of the Taurid Complex (TC). 51 of them have useful SLCs and 34 of these (67%) exhibit Cometary activity. This high percentage of active asteroids gives support to the hypothesis of a catastrophe that took place during the Upper Paleolithic (Clube and Napier, 1984), when a large short-period Comet, arriving in the inner Solar System from the Kuiper Belt, experienced, starting from 20 thousand years ago, a series of fragmentations that produced the present 2P/Encke Comet, together with a large number of other members of the TC. The fragmentation of the progenitor body was facilitated by its heterogeneous structure (very similar to a rubble pile) and this also explains the current coexistence in the complex of fragments of different composition and origin. We have found that (2212) Hephaistos and 169P/NEAT are active and members of the TC with their own sub-group. Other components of the complex are groups of meteoroids, that often give rise to meteor showers when they enter the terrestrial atmosphere, and very probably also the two small asteroids that in 1908 and 2013 exploded in the terrestrial atmosphere over Tunguska and Chelyabinsk, respectively. What we see today of the TC are the remnants of a very varied and numerous complex of objects, characterized by an intense past of collisions with the Earth which may continue to represent a danger for our planet.