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1.
The Asteroid Photometric Catalogue was used to redetermine the rotation periods of all asteroids with data in the catalogue. The quality of the period determinations was divided into five groups. The total number of asteroids studied were 710 and 225 of these were considered not to be observed enough to yield any rotation period (code 0). For 121 asteroids the uncertainty was several hours (code d) and for 180 the uncertainty was less than one hour (code c). Code a was used for asteroids with reliable pole determinations (47 asteroids) and code b was used for asteroids with very reliable synodic rotation periods (137 asteroids). Some statistic properties of the rotation periods of asteroids are presented. 相似文献
2.
The thermophysics of asteroids has become an important frontier for the research of asteroids in recent years. In this paper, we have introduced the thermophysical models commonly used in this field, by using these thermophysical models and combining with the data observed by the space or ground-based IR telescopes, some thermophysical parameters of asteroids, such as the thermal inertia, geometric albedo, effective diameter, surface roughness, and surface temperature, etc., can be derived. We have mentioned also the shape model and IR observation of asteroids, as well as the obtained thermophysical parameters for a part of asteroids. These thermophysical parameters can be further applied to studying the asteroids’ Yarkovsky effect, YORP effect, and so on, even can provide the relevant information for the spacecraft landing on the asteroid surface and the return mission of a spacecraft after the asteroid sampling. 相似文献
3.
Close encounters of asteroids with the Earth can lead to a transition to resonant orbits, close encounters, and collisions in the future. The structure of the sets of possible collisions of asteroids with the Earth is similar to a fractal structure thanks to resonant returns of asteroids. Areas of semi-major axes and positions and sizes of gaps leading to collisions with the Earth for Apophis asteroids 2007 VK184 and 2011 AG5 are given. 相似文献
4.
The size distribution of main belt of asteroids is determined primarily by collisional processes. Large asteroids break up and form smaller asteroids in a collisional cascade, with the outcome controlled by the strength-size relationship for asteroids. In addition to collisional processes, the non-collisional removal of asteroids from the main belt (and their insertion into the near-Earth asteroid (NEA) population) is critical, and involves several effects: strong resonances increase the orbital eccentricity of asteroids and cause them to enter the inner planet region; chaotic diffusion by numerous weak resonances causes a slow leak of asteroids into the Mars- and Earth-crossing populations; and the Yarkovsky effect, a radiation force on asteroids, is the primary process that drives asteroids into these resonant escape routes. Yarkovsky drift is size-dependent and can modify the main-belt size distribution. The NEA size distribution is primarily determined by its source, the main-belt population, and by the size-dependent processes that deliver bodies from the main belt. All of these effects are simulated in a numerical collisional evolution model that incorporates removal by non-collisional processes. We test our model against a wide range of observational constraints, such as the observed main-belt and NEA size distributions, the number of asteroid families, the preserved basaltic crust of Vesta and its large south-pole impact basin, the cosmic ray exposure ages of meteorites, and the cratering records on asteroids. We find a strength-size relationship for main-belt asteroids and non-collisional removal rates from the main belt such that our model fits these constraints as best as possible within the parameter space we explore. Our results are consistent with other independent estimates of strength and removal rates. 相似文献
5.
《Chinese Astronomy and Astrophysics》2023,47(1):127-146
The YORP (Yarkovsky-O’Keefe-Radzievskii-Paddack) effect is one of the mechanisms of the long-term dynamical evolution of asteroids. Compared with factors such as collision and gravitational perturbation, the YORP is of small magnitude, and the short-time scale observation effect is inconspicuous, which brings great difficulties to the direct measurement of the YORP. From the Asteroid Lightcurve Database, asteroids having a high confidence rotation period were selected for this study. Two subsample groups for identifying potential asteroids slowed by the YORP effect are provided by using the kernel density estimation method and the Kolmogorov-Smirnov test to analyze the rotation rate distribution characteristics of near-Earth asteroids and main belt asteroids; a screening model is proposed based on the light-curve data of seven YORP asteroids with YORP rotation acceleration, combined with the YORP intensity estimation method and the detection conditions of the YORP effect. Finally, ten candidates that can directly detect the YORP effect through light-curve data in the future are listed based on the screening model. 相似文献
6.
Wing-Huen IP 《Astrophysics and Space Science》1975,38(2):475-481
The possibility of incorporating the resonant effect and jet stream formation process into the problems of the Hilda asteroids and Kirkwood gaps is discussed qualitatively. It appears that formation of the precursor jet streams of the resonant asteroids in the main belt would be suppressed due to the collisional perturbation effect of the ambient matter in this region. Together with the biased distribution of near-resonant asteroids, the depletion across the Kirkwood gaps could be understood. Within the context of jet stream theory the existence of Hilda asteroids outside the main belt requires the original limit of the main belt to be not much more extensive than the present value of 3.5 AU. This is suggestive of a cosmogonic origin of the observed outer limit. 相似文献
7.
At present, approximately 1500 asteroids are known to evolve inside or sticked to the exterior 1:2 resonance with Mars at a ? 2.418 AU, being (142) Polana the largest member of this group. The effect of the forced secular modes superposed to the resonance gives rise to a complex dynamical evolution. Chaotic diffusion, collisions, close encounters with massive asteroids and mainly orbital migration due to the Yarkovsky effect generate continuous captures to and losses from the resonance, with a fraction of asteroids remaining captured over long time scales and generating a concentration in the semimajor axis distribution that exceeds by 20% the population of background asteroids. The Yarkovsky effect induces different dynamics according to the asteroid size, producing an excess of small asteroids inside the resonance. The evolution in the resonance generates a signature on the orbits, mainly in eccentricity, that depends on the time the asteroid remains captured inside the resonance and on the magnitude of the Yarkovsky effect. The greater the asteroids, the larger the time they remain captured in the resonance, allowing greater diffusion in eccentricity and inclination. The resonance generates a discontinuity and mixing in the space of proper elements producing misidentification of dynamical family members, mainly for Vesta and Nysa-Polana families. The half-life of resonant asteroids large enough for not being affected by the Yarkovsky effect is about 1 Gyr. From the point of view of taxonomic classes, the resonant population does not differ from the background population and the excess of small asteroids is confirmed. 相似文献
8.
YORP (Yarkovsky-O''Keefe-Radzievskii-Paddack)效应是小行星长期动力学演化的机制之一. 与碰撞、引力摄动等因素相比, YORP效应作用量级小, 短时标观测效应不明显, 这给直接测量YORP效应带来了很大的困难. 利用小行星光变数据库中已知的小行星数据, 统计了小行星的自转速率分布, 使用核密度估计以及Kolmogorov-Smirnov检验分别分析了近地小行星和主带小行星自转速率的分布特性, 分别给出了在近地小行星和主带小行星中寻找受YORP效应影响减速自转的最佳样本群; 基于7颗已被探测到YORP旋转加速度的近地小行星, 利用YORP强度估计方法和光变探测条件建立了筛选模型, 给出了未来可直接通过光变数据探测\lk YORP效应的10颗近地小行星. 相似文献
9.
The mean UBV color of S-class asteroids varies markedly with distance from the Sun and may also vary with diameter, implying either that the surface properties of the asteroids have been modified by space weathering or, as suggested here, that there are least two major subclasses of S-class asteroids with different mean locations. 相似文献
10.
T. A. Heppenheimer 《Celestial Mechanics and Dynamical Astronomy》1980,22(3):297-304
It is proposed that the Kirkwood Gaps are primordial, representing regions where asteroids failed to form by accretion. A brief scenario is presented to indicate the main features of a model for the early history of the asteroids. An analytical treatment is given for the effects of a solar nebula upon the eccentricity-pumping of asteroids, due to secular perturbations and to commensurability-type resonances associated with Jupiter. It is shown that nebular effects promote growth of main-belt asteroids; but in commensurability regions, growth is inhibited. A discussion is given of two related problems: the origin of asteroidal eccentricities and inclinations, and the likelihood that Jupiter suffered major changes in its semimajor axis during its formation. It is suggested that in view of these problems, the present theory should not be taken as necessarily correct, but should be regarded as illustrative of viewpoints which in time may yield a correct theory. 相似文献
11.
We have shown that the least reliable data source for estimating the albedo of asteroids is the maximal value of the degree of negative polarization. To increase the accuracy of the method that uses the data on the slope of the positive branch of polarization, the values of the approximating coefficient should be selected in accordance with a specified type of asteroids. The similar situation is in the shadow method, where the value of the phase integral q should be selected in accordance with each of the types. Moreover, the estimates obtained by both methods will be more reliable if the phase dependences of brightness that are characteristic of a specified type of asteroids, including the range of the opposition effect, are used in transforming from A(0) to A(α). The modeling performed with the Irvine-Yanovitskii modification of the shadow model of Hapke showed that the values of the phase coefficient β (10° ≤ α ≤ 20°) and q are, respectively, in the ranges of 0.016–0.030 and 0.6–1.0 for the E-type asteroids, 0.026–0.033 and 0.42–0.52 for the M-type asteroids, and 0.031–0.039 and 0.42–0.52 for the C-type asteroids. 相似文献
12.
The Asteroid Photometric Catalogue was used to redetermine the rotation periods of all asteroids with data in the catalogue. The quality of the period determinations was divided into five groups. The total number of asteroids studied were 710 and 225 of these were considered not to be observed enough to yield any rotation period (code 0). For 121 asteroids the uncertainty was several hours (code d) and for 180 the uncertainty was less than one hour (code c). Code a was used for asteroids with reliable pole determinations (47 asteroids) and code b was used for asteroids with very reliable synodic rotation periods (137 asteroids). Some statistic properties of the rotation periods of asteroids are presented. 相似文献
13.
The masses of 27 asteroids are found from optical and radar observations of perturbed asteroids (test particles). The masses of 18 objects have been previously determined by other authors in the construction of ephemerides EPM2011, DE423, and INPOP10a. Their values are based on observations of the delay time of radio signals from spacecraft. Our values have smaller errors for most of the asteroids. Comparing our results with the latest determinations based only on optical observations of asteroids also shows their accuracy. 相似文献
14.
A scientific collaboration between TÜB?TAK National Observatory (Turkey), Kazan State University (Russia) and Nikolaev Astronomical Observatory (Ukraine) involves observations of minor planets and near-Earth asteroids (NEAs) with the 1.5 m Russian-Turkish telescope (RTT150). Regular observations of selected asteroids in the range of 11-18 magnitudes began in 2004 with the view of determining masses of selected asteroids, improving the orbits of the NEAs, and studying physical characteristics of selected asteroids from photometric observations. More than 3000 positions of 53 selected asteroids and 11 NEAs have been obtained with an internal error in the range of 30-300 mas for a single determination. Photometric reductions of more than 4000 CCD frames are in progress. Masses of 21 asteroids were estimated through dynamical method using the ground-based optical observations, mainly from the RTT150 and Minor Planet Center. A comparison of the observational results from the RTT150 in 2004-2005 with observations of the same objects at other observatories allows us to conclude that RTT150 can be used for ground-based support in astrometry for the space mission GAIA. 相似文献
15.
Kent D. Trego 《Earth, Moon, and Planets》1991,53(3):233-235
A survey of current near-Earth asteroids and inner solar system comets suggests C class asteroids may have been the impactors during the Archean period resulting in the formation of spherule beds because of their carbonaceous composition and large diameters. 相似文献
16.
T. A. Heppenheimer 《Earth, Moon, and Planets》1978,18(4):491-498
Among the major features of the asteroids as a group is the fact that they are small and numerous rather than being a single planet, and that they have unusually high eccentricities and inclinations. Regarding the first, this paper presents two lines of argument concerning the concept that the asteroids formed with a mass-distribution similar to what we observe today. Considerations of planet accretion are used to clarify the role of Jupiter in preventing coalescence of asteroids into a single planet. Regarding the eccentricities and inclinations, it is proposed that they were excited by secular resonances associated with the presence of Jupiter within a dissipating solar nebula. 相似文献
17.
Jan Svoren Marek Husarik Jaroslav Ambroz Jiri Drbohlav Jaroslav Medek 《Earth, Moon, and Planets》2009,105(2-4):361-365
A semi-automated photometric telescope built at the Skalnate Pleso Observatory is described. In December 2000, the 0.3-m f/5 Zeiss astrograph was replaced by a 0.61-m f/4.3 mirror telescope equipped with a CCD camera. The observing programme is created to conform to the photometry of asteroids which are suspected to be of binary nature; photometry of NEAs and MBAs; a long-term photometry for theoretical modelling of the shape of asteroids; and photometry and astrometry of active comets and asteroids. Some results concerning the binary character of the asteroids are described in the paper. 相似文献
18.
René Duffard 《Earth, Moon, and Planets》2009,105(2-4):221-226
19.
We present results on the identification of two new V-type asteroids, 809 Lundia and 956 Elisa. These asteroids are located in the neighborhood of Asteroid 4 Vesta, but they do not belong to Vesta's dynamical family. Their spectra in the visible wavelength are consistent with the spectra of the Vesta family members (Vestoids) and of other V-type objects in the nearby region too. The possible existence of two spectroscopic groups of V-type asteroids in the Vesta region is discussed. 相似文献
20.
M.Ju. Sokolskaya 《Planetary and Space Science》1997,45(12):1575-1580
A modified Laplacian technique is described for initial orbit determination of asteroids from CCD observations and its applications for orbit determination of the main belt asteroids and near Earth asteroids. The proposed modification is based on a simultaneous improvement of both the orbital elements and the derivatives of spherical coordinates in frames of Laplace's method. It provides an orbit which represents the used observations with the residuals comparable with errors of these observations. The improved values of the derivatives might be used as ephemeris parameters for identification of newly discovered objects. 相似文献