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This paper explores parallelism performance for C, C++, Go, Java, Julia, and Rust on N-body simulations. We begin with a basic O(N2) simulation for each language based on the n-body benchmark in the Benchmark Game. The original benchmark is adjusted to include a larger number of particles and run in parallel. We also add parallelism to the force calculations using a kD-tree. This work builds on previous work by including parallelism and adding the Julia programming language to our survey. We find that for straight number-crunching, all of these languages provide similar performance, and all have sufficient support for parallelism that runtimes scale well with thread counts. On the other hand, when a spatial data structure, such as the kD-tree, is introduced, the runtimes vary dramatically between languages. In that situation, Julia’s performance looks more like Python, taking over 100 times as long as Rust/C/C++ to finish. Rust comes out on top with an impressive 50% lead over C and C++. 

Abstract The discovery of two thin rings around the ∼ 250 km sized Centaur Chariklo was the first of its kind, and their formation and evolutionary mechanisms are not well understood. Here, we explore a single shepherd satellite as a mechanism to confine Chariklo’s rings. We also investigate the impact of such a perturber on reaccretion, which is a likely process for material located outside the Roche limit. We have modifiedN-body code that was developed for Saturn’s rings to model the Chariklo system. Exploration of a reasonable parameter space indicates that rings like those observed could be stable as the result of a single satellite with a mass of a few ×10¹³kg that is in orbital resonance with the rings. There is a roughly linear relationship between the model optical depth and the mass of the satellite required to confine a ring. Ring particles do not accrete into moonlets during hard-sphere simulations. However, a reasonable fraction of the ring material forms into moonlets after a few tens of orbits for soft-sphere collisions. The ring-particle properties are thus key parameters in terms of moonlet accretion or destruction in this system. 

Abstract A stellar occultation of Gaia DR3 2646598228351156352 by the Centaur (2060) Chiron was observed from the South African Astronomical Observatory on 2018 November 28 UT. Here we present a positive detection of material surrounding Chiron from the 74-inch telescope for this event. Additionally, a global atmosphere is ruled out at the tens of microbars level for several possible atmospheric compositions. There are multiple 3σdrops in the 74-inch light curve: three during immersion and two during emersion. Occulting material is located between 242 and 270 km from the center of the nucleus in the sky plane. Assuming the ring-plane orientation proposed for Chiron from the 2011 occultation, the flux drops are located at 352, 344, and 316 km (immersion) and 357 and 364 km (emersion) from the center, with normal optical depths of 0.26, 0.36, and 0.22 (immersion) and 0.26 and 0.18 (emersion) and equivalent widths between 0.7 and 1.3 km. This detection is similar to the previously proposed two-ring system and is located within the error bars of that ring-pole plane; however, the normal optical depths are less than half of the previous values, and three features are detected on immersion. These results suggest that the properties of the surrounding material have evolved between the 2011, 2018, and 2022 observations.