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1.
A procedure of selection of meteoroids from major streams is suggested and applied to the IAU Lund photographic database modified by a check for internal consistency among orbital elements (3411 orbits). Limits for choice of stream members were defined by break points on the plots of the cumulative numberN
C vs. the Southworth-HawkinsD discriminant. For the break points were considered the points from which the dependenceN
C vs.D changes to a quasi-linear one, and with the increasingD, N
C changes only moderately. Except for the Taurids which desire a separate analysis, theN
C vs.D diagrams are presented for the following major meteoroid streams: Quadrantids, Lyrids, Aquarids, Capricornids, N and S Aquarids, Perseids, Orionids, Leonids and Geminids. The mean orbits, velocities and radiants of the streams are derived and compared with the osculating orbits of their parent bodies. The limitingD
B was found to be a function of the number of the stream membersN
CB. Omitting the exceptionally concentrated Geminids, the relation is in the formD
B = 0.058 *ln(N
CB) – 0.04. 相似文献
2.
D. I. Steel 《Earth, Moon, and Planets》1995,68(1-3):13-30
Various points are discussed concerning the association of Earth-crossing asteroids (ECAs) with meteoroid streams, including the drawbacks of the techniques used in some previous work. In comparing the theoretical radiants of any ECA (or, indeed, comet) with observed meteor radiants it is necessary that the orbit used be that appropriate for epochs when the ECA has a node at 1 AU; in each precession cycle of the argument of perihelion () there will be four values rendering a node at the Earth's orbit, so that four showers are expected. Precession of the node will result in sets of showers at different times of year from different-precession cycles, whilst for some objects the orbital evolution is more convoluted. For diffuse, low-flux showers a problem is differentiating the meteors associated with any ECA from the sporadic background; a new graphical technique is introduced for illuminating whether such associations exist. A re-evaluation is required of whether ECAs should be thought of as being parent bodies of specific showers. Although this might be the case for some very large ECAs (such as (3200) Phaethon, associated with the Geminid stream), the bodies observed now being extinct or dormant cometary cores, it is suggested that in general the ECAs are better thought of as being large fragments produced in hierarchical cometary disintegrations. That is, some ECAs are just the largest meteoroids in meteoroid streams. 相似文献
3.
. , , . , t>1010 ( z<105) .
In this paper we continue the work of Weymann, investigating the causes of distortion of the spectrum of the residual radiation from the Planck curve. We discuss the distortion to the spectrum, resulting from recombination of primeval plasma.We then derive an analytic expression for the distortion to the equilibrium spectrum due to Compton scattering by hot electrons. On the basis of the observational data we conclude that a period of the existence of neutral hydrogen is inescapable in the hot model of the universe. It is concluded that any injection of energy att>1010 sec (red shiftz<105) give the distortions of the equilibrium spectrum.相似文献
4.
We numerically study the bifurcations of two nonlinear maps, with the same linear part, which depend on a parameter namely the Hénon quadratic map and the so called beam-beam map. Many families of periodic orbits which bifurcate from the central family, are studied. Each family undergoes a sequence of period doubling bifurcations in the quadratic map, But the behavior of the beam-beam map is completely different. Inverse bifurcations occur in both maps. But some families of the same type which bifurcate inversely in the quadratic map do not bifurcate inversely in the beam-beam map, even though both maps have common linear part. 相似文献
5.
- . . , . , . 相似文献
6.
J. B. Eades Jr. 《Celestial Mechanics and Dynamical Astronomy》1977,16(3):315-342
In this paper station-keeping is regarded as the specialization of relative motion referred to a moving, orbiting origin. For this study a well-known linear solution to this problem serves as a base formulation from which the investigation begins.Even though the overall problem could be separated into three parts—necessitating two distinct studies for coverage—this paper examines only the last phase of the operation. That is, it is the continuation, or retention, of a relative motion sub-orbit which is of interest in this analysis.The situation becomes one of determining what is needed to maintain the sub-orbit, and/or to adjust it. In addition, the consequences of these actions, and the results predicted from theory are established, examined, and commented upon. In the presentation of information gathered from this study, various graphs have been prepared; however, these are expressed in a dimensionless format so that the results apply equally to all reasonable reference orbits.For this analysis the separate and combined influences, due to both the initial relative motion state and to a thrusting condition, are examined. Also, the consequences of referencing the acquired sub-orbits to an inertially aligned frame of reference (rather than the familiar rotating one) are illustrated, discussed, and commented upon.Formerly: Sr. Analyst and Manager, Seabrook Office, AMA, Inc., Seabrook, Md., U.S.A. 相似文献
7.
, . () . , , , . ( ), , , . . (2.7). ( 1 k
1 ,V — , — .) (k
1) (k) §2 ( (2.14)). , (3.6) (3.4), (3.8) . (3.9)–(3.13) ( (3.9), (3.10) (3.11) , (3.12)–(3.13) ). (3.14), (3.16)–(3.19). - . (3.15). ( (4.14)–(4.15)). (4.23)–(4.25). (4.26)–(4.28). §5. , . ((5.5)–(5.6)). , . (5.10) . 相似文献
8.
The time evolution of interplanetary matter streams is studied using simple mathematical models, taking into account the effects of accretion and fragmentation. While the characteristic behaviour is determined essentiall by 0, the initial ratio of the accretion time scale to the internal collision time scale, a focussing following an initial expansion is generally observed. The relevance of the results to cosmogenic Jet-Streams as well as present day meteor streams is discussed. 相似文献
9.
We report an unsuccessful search for the He+ 4686 line in the low chromosphere. However, at the location of this line we detect a number of other chromospheric emission lines. This leads us to the conclusion that the He+ 4686 identification made in the past, as well as other identifications, are probably in error. Additionally the region of the neutral helium 4713 line is also studied.On leave from Tokyo Astronomical Observatory, Mitaka, Japan. 相似文献
10.
Formulae containing the elements of the variational matrix are obtained which determine the linear iso-energetic stability parameters of periodic orbits of the general three-body problem. This requires the numerical integration of the variational equations but produces the stability parameters with the effective accuracy of the numerical integration. The procedure is applied for the determination of horizontally critical orbits among the members of sets of vertical-critical periodic orbits of the threebody problem. These critical-critical orbits have special importance as they delimit the regions in the space of initial conditions which correspond to possibly stable three-dimensional periodic motion of low inclination. 相似文献
11.
When solar wind plasma in the trailing (eastern) edge of a high-speed stream is mapped back to its estimated source in the high corona using the constant radial velocity (EQRH) approximation, a large range of velocities appears to come from a restricted range in longitude, often only a few degrees. This actually constitutes a sharp eastern coronal boundary for the solar wind stream source, and demands that the boundary have a three-dimensional structure. Using interplanetary data, we infer a systematic variation in source altitude (identified approximately with the Alfvén point), with faster solar wind attaining its interplanetary characteristics at lower altitudes. This also affects the accuracy of the source longitude estimates, so that we infer a width in the high corona of 4–6° for the source of the trailing edges of streams which appear to originate from a single longitude. We demonstrate that the possible systematic interplanetary effects (in at least some cases) are not large ( 2° in heliocentric longitude). The relatively sharp boundaries imply that high-speed streams are well-defined structures all the way down to their low coronal sources, and that the magnetic field structure controls the propagation of the plasma through the corona out to the vicinity of the Alfvén point ( 20 R
). 相似文献
12.
Two new Th ii lines have been identified in the spectrum of the solar photosphere. The abundance derived from these lines together with the previously known Th ii line at 4019 Å, is log
Th = 0.85 ± 0.20 in the log
H = 12.00 scale. Analysis of three Pb i lines in the photospheric spectrum resulted in an abundance of log
pb = 1.90 ± 0.10. The solar Th/Pb ratio is:
Th/
Pb = 0.09
-0.005
0.09
. 相似文献
13.
P. G. Kazantzis 《Astrophysics and Space Science》1979,61(2):477-486
Families of three-dimensional axisymmetric periodic orbits are determined numerically in the Sun-Jupiter case of the restricted three-body problem. These families bifurcate from the vertical-critical orbits (v = 1,b
v = 0) of the basic plane familiesi andI. Further the predictor-corrector procedure employed to reveal these families has been described and interesting numerical results have been pointed out. Also, computer plots of the orbits of these families have been shown in conical projections. 相似文献
14.
G. Contopoulos 《Celestial Mechanics and Dynamical Astronomy》1986,38(1):1-22
We study the bifurcations of families of double and quadruple period orbits in a simple Hamiltonian system of three degrees of freedom. The bifurcations are either simple or double, depending on whether a stability curve crosses or is tangent to the axis b=–2. We have also generation of a new family whenever a given family has a maximum or minimum or .The double period families bifurcate from simple families of periodic orbits. We construct existence diagrams to show where any given family exists in the control space (, ) and where it is stable (S), simply unstable (U), doubly unstable (DU), or complex unstable (), We construct also stability diagrams that give the stability parameters b1 and b2 as functions of (for constant ), or of (for constant ).The quadruple period orbits are generated either from double period orbits, or directly from simple period orbits (at double bifurcations). We derive several rules about the various types of bifurcations. The most important phenomenon is the collision of bifurcations. At any such collision of bifurcations the interconnections between the various families change and the general character of the dynamical system changes. 相似文献
15.
Koujun Yamashita 《Astrophysics and Space Science》1968,2(1):4-22
Rocket-borne photon counters sensitive to bands 1060–1180, 1230–1350, and 1350–1480 were used to measure the celestial ultraviolet radiation above the terrestrial atmosphere. The energy spectra of six objects, Leo, CMa, Ori, , , Ori (combined), Ori, and Tau were obtained. The comparison of them with those calculated with the stellar model atmospheres indicates the deficiency of about 1 mag. in the ultraviolet region, when corrected for interstellar extinction, for all stars except Tau. The observed spectrum of Tau agreed with the theoretical one for normal interstellar extinction. The effects of line blanketing were examined for B1 and B2 stars, and found to account for a part of the difference between the observed and the theoretical values. 相似文献
16.
V. V. Zaitsev 《Solar physics》1971,20(1):95-105
An interpretation is suggested for the rain type radio bursts on the basis of a pulsating regime of the stream instability. This regime may occur in ejected stabilized ion streams trapped in the region in which the magnetic field of the corona has a typical bipolar structure. 相似文献
17.
Minor bodies that, at the present stage, have orbital characteristics similar to those of the Pribram meteorite and that differ from it in the date of activity of the radiants by no more than a 1.2-month period in either direction were detected on the basis of catalog data on the orbits of asteroids, individual fireballs, and fireball and meteor streams obtained from photographic observations. The following objects comprising the Prbram family are among such minor bodies: three asteroids (1863, 4486, and J98S70J) of the Apollo group, three fireball streams, five meteor streams, and ten fireballs. This extensive system of bodies consists of three branches: a Northern (N), an Ecliptical (Q), and a Southern (S) Branch. The family of meteor streams associated with the periodic comet Pons–Winnecke appears to be related to this family. Thus, there emerges an intricate complex of small bodies that is similar to the well-known Taurid complex. In the distribution of various populations of minor bodies according to the quantity c of the Tisserand criterion, both of these complexes of minor bodies, like the group of cometoids (or cometlike asteroids), are situated in the region of unstable motion or, to be more exact, near the gap that arises in the L
2 and L
3 collinear points of libration. 相似文献
18.
The main goal of this paper is to show that the elliptic restricted three-body problem has ejection-collision orbits when the mass parameter µ is small enough. We make use of the blow up techniques. Moreover, we describe the global flow of the elliptic problem when µ = 0 taking into account the singularities due to collision and to infinity. 相似文献
19.
Roberto Viotti Giovanni Battista Baratta Anna Rosa Marenzi Marcello Ranieri 《Astrophysics and Space Science》1990,169(1-2):95-100
We give an overview of the Car phenomenon on the basis of ground and space observations. We discuss in particular the IRAS images. We conclude that Car, initially with a mass > 100M
, is presently an intermediate-type hypergiant withL=5×106
L
, in a rapid evolutionary stage. This phase started with a large increase of mass loss in mid-1800 followed by dust condensation and a large visual fading, at constant bolometric luminosity.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
20.
Kathleen Connor Howell 《Celestial Mechanics and Dynamical Astronomy》1984,32(1):53-71
A largely numerical study was made of families of three-dimensional, periodic, halo orbits near the collinear libration points in the restricted three-body problem. Families extend from each of the libration points to the nearest primary. They appear to exist for all values of the mass ratio , from 0 to 1. More importantly, most of the families contain a range of stable orbits. Only near L1, the libration point between the two primaries, are there no stable orbits for certain values of . In that case the stable range decreases with increasing , until it disappears at =0.0573. Near the other libration points, stable orbits exist for all mass ratios investigated between 0 and 1. In addition, the orbits increase in size with increasing . 相似文献