153 research outputs found
Fragmentation and densities of meteoroids
Photographic observations of meteors carried out in Dushanbe by the method of instantaneous exposure have shown clearly that meteoroids entering the Earth's atmosphere are subjected to different types of fragmentation. The quasi-continuous fragmentation of meteoroids is mostly widespread. Using the physical theory of meteors which takes into account the quasi-continuous fragmentation of meteoroids and on the basis of light curves of meteors the densities of meteoroids of different streams have been determined. The results enable us to conclude that the densities of meteoroids are over an order of magnitude higher than they have been assumed before. Moreover they are close to the densities of carbonaceous and ordinary chondrites
P/Machholz 1986 8 and quadrantid meteoroid stream. Orbital evolution and relationship
The evolution of the P/Machholz's meteoroid stream was simulated. It shows that this stream may produce eight meteor showers. There are the known observed meteor showers such as the Quadrantids, Ursids, Northern and Southern delta-Aquarids, Daytime Arietids, and alpha-Cetids. A satisfactory agreement of the theoretical and observed geocentric radiants and orbits allows one to conclude that the above showers could have been resulted from the decay of the P/Machholz nucleus. The age of the stream is estimated to be 7.5 millennia
Palaeolithic extinctions and the Taurid Complex
Intersection with the debris of a large (50-100 km) short-period comet during
the Upper Palaeolithic provides a satisfactory explanation for the catastrophe
of celestial origin which has been postulated to have occurred around 12900 BP,
and which presaged a return to ice age conditions of duration ~1300 years. The
Taurid Complex appears to be the debris of this erstwhile comet; it includes at
least 19 of the brightest near-Earth objects. Sub-kilometre bodies in meteor
streams may present the greatest regional impact hazard on timescales of human
concern.Comment: 7 pages, 3 figures; accepted for Monthly Notices of the Royal
Astronomical Society (definitive version will be available at
www.blackwell-synergy.com
Military Industrialization of Uzbekistan in 1941—1945
The influence of the Great Patriotic War on the restructuring of the industry of Uzbekistan is considered. The materials of the National Archives of Uzbekistan are used, some of which have not been published before. It is reported that in the pre-war years, the economy of Uzbekistan was dominated by agriculture and the war became a new period of industrialization of the republic. It is stated that during the war years, during the mass evacuation, Uzbekistan received about 190 industrial enterprises from the western regions of the USSR. It is stated that such a large-scale evacuation of industry, on the one hand, created difficulties associated with the placement of equipment and people, and on the other hand, formed a disproportionately expanded industrial potential of Uzbekistan. Attention is focused on the fact that the economy withstood the main difficulties of restructuring industry on a war footing. It is proved that the new industrial centers of the country began to be of great importance for the military economy of the USSR. It is emphasized that the people of Uzbekistan heroically worked on the construction of new plants and factories, as well as on the restoration of evacuated enterprises, which, among other things, made it possible to solve the issue of a stable supply of the army with weapons, and the industry with raw materials and minerals
Identification of a new short-period comet near the sun
We present the identification of comet C/1999 R1 (SOHO) with comet C/2003 R5
(SOHO). Both apparitions were only observed with the Solar and Heliospheric
Observatory (SOHO) at distances smaller than 0.1 AU from the sun with the LASCO
coronagraphs onboard the spacecraft. Although SOHO comets usually have poor
orbital coverage, the 1999 and 2003 arcs are sufficient to generate a link that
seems to satisfy all observations. We also analyze comet C/2002 R5 (SOHO) which
has similar orbital elements. A fragmentation scenario is proposed and
discussed which would support the linkage of C/1999 R1 and C/2003 R5 and thus
its short periodic nature.Comment: 5 pages, 1 figure; accepted for publication in A&
Orbital Elements of Comet C/1490 Y1 and the Quadrantid shower
The Quadrantid shower, one of the most intense showers, has been observed at
the beginning of January each year. However, the origin of the meteors is still
unknown. It was Hasegawa (1979) who first suggested comet C/1490 Y1 to be the
likely origin of the shower based on the historical records of East Asia. We
analyse the records of Jo-Seon-Wang-Jo-Sil-Lok (the Annals of the Joseon
Dynasty in ancient Korea) and calculate the preliminary orbital elements of
comet C/1490 Y1 using a modified Gauss method. We find that comet C/1490 Y1 was
a periodic one and its orbital path was very similar to that of the Quadrantid
meteor stream. The determined orbital elements are perifocal passage time
Tp=2265652.2983 days (7.8 Jan. 1491 in UT), perifocal distance q=0.769 AU,
eccentricity e=0.747, semimajor axis a=3.04 AU, argument of the perifocus
omega=164.03 degrees, longitude of ascending node Omega=283.00 degrees, and
inclination i=70.22 degrees for the epoch of J2000.0. We, therefore, conclude
that our result verifies the suggestion that the comet C/1490 Y1 is the origin
of the Quandrantid meteor shower, but was a periodic comet. We dicuss a
possible link between this comet and the asteroid 2003 EH1 as well.Comment: 7 pages, 2 figures, accepted for publication in MNRA
Meteor light curves: the relevant parameters
We investigate a uniform sample of 113 light curves (LCs) of meteors
collected at the Wise Observatory in November 2002 while observing the Leonid
meteor shower. We use previously defined descriptors such as the skewness F and
a recently defined pointedness parameter along with a number of other
measurable or derived quantities to explore the parameter space in search of
meaningful LC descriptors. We make extensive use of statistical techniques to
reveal links among the variables and to understand their relative importance.
In particular, we show that meteors with long-duration trails rise slowly to
their maximal brightness and also decay slowly from there while showing milder
flaring than other meteors. Early skewed LCs show a fast rise to the peak. We
show that the duration of te luminous phase of the meteor is th emost important
variable differentiating among the 2002 LCs. The skewness parameter F appears
only as the 2nd or 3rd in explaining the LC variance. We suggest that the
pointedness parameter P could possibly be useful to discriminate among meteors
from different showers, or to compare observations and model predictions.Comment: 10 pages (2 figures) in press with MNRA
Electrical Properties of Organic Semiconductor Orange Nitrogen Dye Thin Films Deposited from Solution at High Gravity
In this study the electrical properties of organic semiconductor orange nitrogen dye (OND) have been
examined. Thin film samples were deposited from OND solution in water on a nickel substrate (it was the
first electrode) at room temperature at different gravity conditions including, 1 g (reference samples), 123 g, 277 g and 1107 g by a centrifugal machine. As a second electrode of the samples a gallium drop was used. The voltage-current characteristics of the samples were measured at temperature interval of 30 °C
60 °C. It was found that all voltage-current characteristics were asymmetrical with slightly rectification behavior. The resistances of the samples decrease monotonously with temperature but with acceleration they show minimum around of 123 g. As a rule the forward bias resistance (+ voltage was applied to gallium) were less than reverse bias ones (+ voltage was applied to nickel). The electric behavior of the samples analyzed by the conception of space-charge limited currents (SCLC) at the presence of two different kinds of metallic electrodes (Ni and Ga) in the samples
1999 Quadrantids and the lunar Na atmosphere
Enhancements of the Na emission and temperature from the lunar atmosphere
were reported during the Leonids meteor showers of 1995, 1997 and 1998. Here we
report a search for similar enhancement during the 1999 Quadrantids, which have
the highest mass flux of any of the major streams. No enhancements were
detected. We suggest that different chemical-physical properties of the Leonid
and Quadrantid streams may be responsible for the difference.Comment: 5 pages, 1 figure, accepted for publication in MNRA
Observations of 1999 YC and the Breakup of the Geminid Stream Parent
Apollo asteroid 1999 YC may share a dynamical association with the
Phaethon-Geminid stream complex (Ohtsuka et al. 2008). Here, we present
photometric observations taken to determine the physical properties of 1999 YC.
The object shows a nearly neutral reflection spectrum, similar to but slightly
redder than related objects 3200 Phaethon and 2005 UD. Assuming an albedo equal
to 3200 Phaethon's we find that the diameter is 1.4+/-0.1 km. Time-resolved
broad-band photometry yields a double-peaked rotational period of
4.4950+/-0.0010 hr while the range of the lightcurve indicates an elongated
shape having a projected axis ratio near 1.9:1. Surface brightness models
provide no evidence of lasting mass loss of the kind seen in active short
period cometary nuclei. An upper limit to the mass loss is set at about 0.001
kg/s, corresponding to an upper limit on the fraction of the surface that could
be sublimating water ice of 0.001. If sustained over the 1000 yr age of the
Geminid stream, the total mass loss from 1999 YC (3e7 kg) would be small
compared to the reported stream mass (1e12 - 1e13 kg), suggesting that the
stream is the product of catastrophic, rather than steady-state, breakup of the
parent object.Comment: 36 pages, 8 figures, in press at Astronomical Journa
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