P. Descamps, F. Marchis, J. Durech, J. Emery, A. W. Harris, M. Kaasalainen, J. Berthier, J. -P. Teng-Chuen-Yu, A. Peyrot, L. Hutton, J. Greene, J. Pollock, M. A… 展开作者
P. Descamps, F. Marchis, J. Durech, J. Emery, A. W. Harris, M. Kaasalainen, J. Berthier, J. -P. Teng-Chuen-Yu, A. Peyrot, L. Hutton, J. Greene, J. Pollock, M. Assafin, R. Vieira-Martins, J. I. B. Camargo, F. Braga-Ribas, F. Vachier, D. E. Reichart, K. M. Ivarsen, J. A. Crain, M. C. Nysewander, A. P. Lacluyze, J. B. Haislip, R. Behrend, F. Colas, J. Lecacheux, L. Bernasconi, R. Roy, P. Baudouin, L. Brunetto, S. Sposetti, F. Manzini
我们报告的结果，为期六个月的测光研究的主带二进制C型小行星121赫敏，在其2007年的反对。我们利用了2007年6月赫敏的一个年度春分点所提供的难得的观测机会。春分为地球上的观察者提供了一个侧面，这非常适合对赫敏的身体特征进行彻底的研究。在这项工作中提出的小望远镜进行的观测目录，连同新的自适应光学（AO）的图像之间获得的2005年和2008年与Yepun 8米甚大望远镜和10米凯克望远镜。最引人注目的结果是证实了赫敏是一个分叉和细长的身体，正如Marchis等人所建议的那样，（2005年）。根据AO、测光和热观测的组合计算出新的有效直径为187 +/- 6公里。新的直径比迄今为止公认的基于IRAS数据的辐射直径小10%左右。这种差异的原因是IRAS几乎是从极上观测到的。斯皮策太空望远镜的新热观测结果与AO和光变曲线观测得出的直径一致。根据对直径32公里的小卫星进行的新的AO天体测量观测，我们改进了轨道解，并得出赫敏的体积密度的新值为1.4 + 0.5/-0.2 g cm-3。我们推断宏观孔隙度约为33 + 5/-20%。
英文摘要：
We report on the results of a six-month photometric study of the main-belt binary C-type asteroid 121 Hermione, performed during its 2007 opposition. We took advantage of the rare observational opportunity afforded by one of the annual equinoxes of Hermione occurring close to its opposition in June 2007. The equinox provides an edge-on aspect for an Earth-based observer, which is well suited to a thorough study of Hermione's physical characteristics. The catalog of observations carried out with small telescopes is presented in this work, together with new adaptive optics (AO) imaging obtained between 2005 and 2008 with the Yepun 8-m VLT telescope and the 10-m Keck telescope. The most striking result is confirmation that Hermione is a bifurcated and elongated body, as suggested by Marchis et al., (2005). A new effective diameter of 187 +/- 6 km was calculated from the combination of AO, photometric and thermal observations. The new diameter is some 10% smaller than the hitherto accepted radiometric diameter based on IRAS data. The reason for the discrepancy is that IRAS viewed the system almost pole-on. New thermal observations with the Spitzer Space Telescope agree with the diameter derived from AO and lightcurve observations. On the basis of the new AO astrometric observations of the small 32-km diameter satellite we have refined the orbit solution and derived a new value of the bulk density of Hermione of 1.4 +0.5/-0.2 g cm-3. We infer a macroscopic porosity of ~33 +5/-20%.
Anticipating Formation Trends of Binary and Multiple Asteroids in the Main Asteroid Belt Due to Electric Discharge Effects by Using the relation of the Sun's Activity and Binary Asteroids Aggregation Statistics
Context. Small binary asteroid systems and pairs are thought to form through fission induced by spin up via the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect. This process is expected to depend on their structural strength, hence composition. Aims. We aim to determine how taxonomic classes, used as a proxy for composition, distribute amongst binary asteroids and asteroid pairs compared to the general population. Methods. We compare the distribution of taxonomic classes of binary systems and pairs with that of a reference sample of asteroids. We build this sample by selecting asteroids to…
Most close-in planetary satellites are in synchronous rotation, which is usually the stable end-point of tidal despinning. Saturn's moon Hyperion is a notable exception by having a chaotic rotation. Hyperion's dynamical state is a consequence of its high eccentricity and its highly prolate shape (Wisdom et al. 1984). As many binary asteroids also have elongated secondaries, chaotic rotation is expected for moons in eccentric binaries (Ćuk and Nesvorný, 2010), and a minority of asteroidal secondaries may be in that state (Pravec et al. 2016). The question of secondary rotation is also important…
Synchronous binary asteroids can experience libration about their tidally-locked equilibrium, which will result in energy dissipation. This is an important topic to the Asteroid Impact and Deflection Assessment, where excitation caused by the DART kinetic impact in the Didymos binary asteroid system may be reduced through dissipation before Hera arrives to survey the effects of the impact. We develop a numeric model for energy dissipation in binary asteroids to explore how different system configurations affect the rate of energy dissipation. We find tumbling within the synchronous state elimi…
Resonant Networks of Spin-Orbit Coupling in Ellipsoid-Ellipsoid Binary Asteroid Systems
School of Astronomy and Space Science, Nanjing University（南京大学天文与空间科学学院）；Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education, Nanjing University（南京大学现代天文与天体物理教育部重点实验室）
With the inception of gravitational wave astronomy, astrophysical studies using interferometric techniques have begun to probe previously unknown parts of the universe. In this work, we investigate the potential of a new interferometric experiment to study a unique group of gravitationally interacting sources within our solar system: binary asteroids. We present the first study into binary asteroid detection via gravitational signals. We identify the interferometer sensitivity necessary for detecting a population of binary asteroids in the asteroid belt. We find that the space-based gravitatio…
Using viscoelastic mass/spring model simulations, we explore tidal evolution and migration of compact binary asteroid systems. We find that after the secondary is captured into a spin-synchronous state, non-principal axis rotation in the secondary can be long-lived. The secondary's long axis can remain approximately aligned along the vector connecting secondary to primary while the secondary rocks back and forth about its long axis. Inward orbital semi-major axis migration can also resonantly excite non-principal axis rotation. By estimating solar radiation forces on triangular surface meshes,…
NASA's Double Asteroid Redirection Test (DART) mission will kinetically impact Dimorphos, the secondary component of the Didymos binary asteroid system, which will excite Dimorphos's dynamical state and lead to significant libration about the synchronous state and possibly chaotic non-principal axis rotation. Although this particular outcome is human caused, many other secondary components of binary systems are also prone to such exotic spin states. For a satellite in an excited spin state, the time-varying tidal and rotational environment can lead to significant surface accelerations. Dependi…
We developed two different point spread function (PSF) analysis techniques for discovering wide separation binary asteroids in wide field surveys. We then applied these techniques to images of main belt asteroids in the 4 to 60 km size range captured by Pan-STARRS1. Johnston (2019) lists fewer than 10 known binaries in this size range with separations greater than 10% of the primary's Hill radius, so discovering more wide binary asteroids is crucial for understanding the limits of binary stability and improving our knowledge of asteroid masses. We analyzed each image by: i) comparing the major…
Binary asteroids probe thermal-radiation effects on the main-belt asteroids' evolution. We discuss the possibility of detecting binary minor planet systems by the astrometric wobble of the center-of-light around the center-of-mass. This method enables the exploration of the phase-space of binary asteroids, which is difficult to explore using common detection techniques. We describe a forward model that projects the center-of-light position with respect to the center-of-mass, as it is seen by the observer. We study the performance of this method using simulated Gaia-like data. We apply the astr…
Increasing observations of white dwarf atmospheric pollution and disrupting planetesimals is driving increased studies into the fate of exo-asteroids around post-main-sequence stars. Planetesimal populations in the Solar System which are most likely to survive the violent post-main-sequence evolution, such as the Kuiper Belt, display a large binary fraction with a propensity for near equal-mass components and provide a previously unexplored population of planetesimals which are likely to exist around white dwarfs. Here we simulate the dynamical evolution of equal-mass binary asteroid systems a…
Simulations of asteroid binaries commonly use mutual gravitational potentials approximated by series expansions, leading to truncation errors, and also preventing correct computations of the forces and torques when the bodies are close. We make of a recently developed method where the mutual potential is calculated with the use of surface integrals and is exact for bodies of ellipsoidal shapes. The solutions produced by the surface integration method are compared with an approach that expands the mutual potential, truncated at second and fourth order. The approximate solutions are generated wi…
We have monitored the Didymos-Dimorphos binary asteroid in spectropolarimetric mode in the optical range before and after the DART impact. The ultimate goal was to obtain constraints on the characteristics of the ejected dust for modelling purposes. Before impact, Didymos exhibited a linear polarization rapidly increasing with phase angle, reaching a level of about 5% in the blue and about 4.5 in the red. The shape of the polarization spectrum was anti-correlated with that of its reflectance spectrum, which appeared typical of an S-class asteroid. After impact, the level of polarization droppe…
This paper continues the authors' previous work and presents a coplanar averaged ellipsoid-ellipsoid model of synchronous binary asteroid system (BAS) plus thermal and tidal effects. Using this model, we analyze the breakup mechanism of the synchronous BAS. Different from the classical spin-orbit coupling model which neglects the rotational motion's influence on the orbital motion, our model considers simultaneously the orbital motion and the rotational motions. Our findings are following. (1) Stable region of the secondary's synchronous state is mainly up to the secondary's shape. The primary…
