| 其他摘要 | Asteroids, leftover of planetesimals from the early solar system, carry information about the primordial nebular material and the evolutionary history of the solar system. The density and mass of asteroids are important parameters for understanding their ori gins and evolution, yet these physical parameters are challenging to determine accu rately. Binary asteroid systems provide a method to explore the internal structure and physical characteristics of distant asteroids. It is theorized that approximately 15% of asteroids in the belt have satellites, but out of the roughly 1.3 million known asteroids, only 245 binary systems have been identified. This suggests that many main belt binary asteroid systems remain undiscovered. Observation and research of these systems allow not only for the measurement of their densities, which infer their internal structures and compositions, but also for insights into their formation and evolutionary processes, ul timately provide information for the origins and evolution of both the asteroid belt and the solar system. Different types of binary asteroid systems, categorized by their structural and dy namical characteristics, suggest varied formation and evolutionary paths. This paper focus on contact binary asteroids, a kind of synchronous binary asteroids whose semi major axes equal the sum of the maximum semi-major axes of the two ellipsoid-shaped asteroids. Several examples of this type have already been identified among other small body classes in the solar system, such as near-Earth asteroids, Trojans, and Kuiper belt objects. In the Yunnan-HongKong survey data, the lightcurve of Main Belt Asteroid (2572) Annschnell exhibited typical contact binary asteroids lightcurve characteristics. For ”rubble pile” asteroids, whose internal structures are loosely bound, the Roche binary asteroid theory provides a framework for analyzing system parameters, including aster oid density. Combining YNHK survey observations with photometric data downloaded from MPC, we analyzed (2572) Annschnell by the Roche binary asteroid model. We devel oped a contact binary asteroid lightcurve inversion program, deriving the best-fit Roche binary model for (2572) Annschnell. The resulting densities of the two bodies, approx imately 3.15 g/cm³, are consistent with those of CV or CK chondrites, supporting the classification of this system as a member of the C-type asteroids. Additionally, we ob tained shape parameters for the primary (𝑎𝑝 = 1.0, 𝑏𝑝 = 0.84,𝑐𝑝 = 0.76) and secondary (𝑎𝑠 = 1.06, 𝑏𝑠 = 0.57, 𝑐𝑠 = 0.53) asteroids. From the normalized rotational angular velocity (Ω = 0.34) and the dimensionless system angular momentum (𝐻 = 0.48), we hypothesize that this contact binary asteroid may have formed through the rotational fission of a single asteroid. The paper is structured as follows: Chapter 1 introduces the significance and his tory of binary asteroid research and discusses the various types of binary asteroids and possible evolutionary mechanisms; Chapter 2 describes detection methods for binary asteroids; Chapter 3 elaborates on Roche binary asteroid theory, providing a theoretical foundation for understanding the formation and dynamical evolution of binary aster oids; Chapter 4 presents the contact binary asteroid luminosity model developed and tests its effectiveness and accuracy; Chapter 5 focuses on the observational data pro cessing and analysis, detailing the procedure for extracting light curves and showcasing the extracted light curve for (2572) Annschnell; and Chapter 6 applies the contact binary asteroid luminosity model to the photometric data of (2572) Annschnell to analyze its best-fit Roche binary model parameters and discuss its origin and composition.Chapter 7 summarizes the entire document and provides an outlook for the future |
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