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11.
The spatial distribution of O-type stars projected onto the Per OB1 association has been investigated. From the limited data available we find evidence to suggest that there are several distinct clusters of early type stars in the association's line of sight. It is found that all those stars identified in the past as being blue stragglers are likely situated in the most distant cluster and consequently they are unlikely to be coevally related to the closer stellar groups. Our argument is that all those stars previously classified as blue stragglers in Per OB1 are normal O and OBN stars. 相似文献
12.
Martin Beech 《Astrophysics and Space Science》1987,138(1):113-119
In this article it is argued that galactic magnetic fields are generated in the earliest moments of galaxy collapse. Our model proposes that provided, even if only briefly, a supermassive star is formed early on in the galaxy formation process, this star can produce a strong centrally localized magnetic field which may act as the seed field from which a galactic field can grow. In order to substantiate this model, detailed numerical calculations will be required. 相似文献
13.
Martin Beech 《Astrophysics and Space Science》1987,132(2):269-276
We consider the time-scale of orbital circularization for those massive binary systems that produce WR+C systems. Using the observation that such systems have acquired circular orbits on a time-scale of the order of the Main-Sequence lifetime of the initial secondary, we estimate the intrinsic time-scale of the tidal interaction 0. We find that the tidal dissipation in such systems is very efficient and that, on the average, 0 ~ 103 yr. 相似文献
14.
Martin Beech 《Monthly notices of the Royal Astronomical Society》1998,294(2):259-264
This study is motivated by the possibility of determining the large-body meteoroid flux at the orbit of Venus. Towards this end, we attempt to estimate the times at which enhanced meteoric activity might be observed in the planet's atmosphere. While a number of meteoroid streams are identified as satisfying common Earth and Venus intercept conditions, it is not clear from the Earth-observed data if these streams contain large-body meteoroids. A subset of the Taurid Complex objects may produce fireball-rich meteor showers on Venus. A total of 11 short-period, periodic comets and 46 near-Earth asteroids approach the orbit of Venus to within 0.1 au, and these objects may have associated meteoroid streams. Comets 27P/Crommelin and 7P/Pons–Winnecke are identified as candidate parents to possible periodic meteor showers at the orbit of Venus. 相似文献
15.
Martin Beech 《Earth, Moon, and Planets》2014,113(1-4):33-41
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
16.
We interpret the historical activity of comet 55P/Tempel–Tuttle in terms of the observed characteristics of present-day short
period comets. In this respect, it is now realized that such comets are liable to undergo significant outburst and mantle
loss events at intervals separated by of order a few hundred years. On this basis one might well expect comet 55P/Tempel–Tuttle
to have undergone several outbursts since its earliest sighing in 1366. The limited absolute magnitude data available for
55P/Tempel–Tuttle is not inconsistent with the suggestion that the comet underwent outbursts during its 1699 and 1865 perihelion
returns. If the outbursts of comet 55P/Tempel–Tuttle are interpreted in terms of mantle loss events then the bright, electrophonic
sound producing fireballs reported during the great Leonid meteor storm of 1833 may have been due to the Earth sampling mantle
material ejected during the outburst of 1699.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
Martin Beech Simona Nikolova J. Jones 《Monthly notices of the Royal Astronomical Society》1999,310(1):168-174
Comet 15P/Finlay is unusual in that, contrary to ab initio expectations, it demonstrates no apparent linkage to any known meteor shower. Using data contained within the Electronic Atlas of Dynamical Evolutions of Short-Period Comets, we evaluate theoretical shower radiants for Comet 15P/Finlay, but find no evidence to link it to any meteoric anomalies in recorded antiquity. This result, however, must be tempered by the fact that any Comet 15P/Finlay-derived meteoroids will have a low, 16 km s−1 , encounter velocity with Earth's atmosphere. Typically, therefore, one would expect mostly faint meteors to be produced during an encounter with a Comet 15P/Finlay-derived meteoroid stream. We have conducted a D -criterion survey of meteoroid orbits derived from three southern hemisphere meteor radar surveys conducted during the 1960s, and again we find no evidence for any Comet 15P/Finlay-related activity. Numerical calculations following the orbital evolution of hypothetical meteoroids ejected from the comet, at each perihelion epoch since 1886, indicate that Jovian perturbations effectively 'drive' the meteoroids to orbits with nodal points beyond the Earth's orbit. The numerical calculations indicate that, even if Comet 15P/Finlay had been a copious emitter of meteoroids during the past 100 years, virtually none of them would have evolved into orbits capable of being sampled by the Earth. There are good observational data, however, to suggest that Comet 15P/Finlay is becoming a transitional comet–asteroid object, and that it has probably not been an efficient producer of meteoroids during the past several hundreds of years. 相似文献
18.
Martin Beech 《Meteoritics & planetary science》2002,37(5):649-660
Abstract— The remarkable fact about the Mazapil meteorite is that it fell on the same night, in 1885, that the Andromedid meteor shower underwent a spectacular outburst. The simultaneity of these two events has driven speculation ever since. From ?1886 to ?1950 the circumstances of the Mazapil fall were taken, by a number of researchers, as the paradigm that demonstrated the fact that comets were actually swarms of meteoritic boulders. Beginning ?1950, however, most researchers began to adopted the stance that the timing of the Mazapil fall was nothing more than pure coincidence. The reason behind this change in interpretation stemmed from, amongst other factors, the fact that none of the prominent annual meteor showers could be clearly shown to deliver meteorites. Also, with the introduction of the icy‐conglomerate model for cometary nuclei, by F. Whipple in the early 1950s, it became increasingly clear that only exceptional circumstances would allow for the presence of large meteoritic bodies in cometary streams. Further, by the mid 1960s it had been shown that meteorites could, in fact, be delivered to the Earth from the main belt asteroid region via gravitational resonances. With the removal of the dynamical “barrier” against the delivery of meteorites from the asteroid region, the idea that the Mazapil meteorite could have been part of the Andromedid stream fell into complete disfavor. This being said, we nonetheless present the results of a study concerning the possible properties of the parent object to the Mazapil meteorite based upon the assumption that it was a member of the Andromedid stream. This study is presented to illustrate the point that while cometary showers do not yield meteorites on the ground, this does not, in fact, substantiate the argument that no meteoritic bodies reside in cometary streams. Indeed, we find no good reason to suppose that an object with the characteristics of the Mazapil meteorite could not have been delivered from the Andromedid stream. However, we argue that upon the basis of the actual reported observations and upon the scientific maxim of minimized hypothesis and least assumption it must be concluded that the timing of the fall of the Mazapil meteorite and the occurrence of the Andromedid outburst were purely coincidental. 相似文献
19.
Martin Beech 《Astrophysics and Space Science》1992,192(2):329-334
The root structure of the Eddington quartic equation is examined in a general manner. The complex and real root topology is annotated, and an explicit expression for the real positive root is derived. 相似文献
20.
Martin Beech 《Astrophysics and Space Science》1985,116(1):207-212
We consider the various methods used to constrain the possible field strength of the present day intergalactic field and findB
0(G)<10–10 as a probable upper bound. It is suggested that the observed intergalactic magnetic field might not be primordial in origin but rather the result of magnetic flux leakage from galaxies and clusters of galaxies. 相似文献