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1. Photometric Properties of Jupiter Trojans Detected by the Dark Energy Survey

   https://doi.org/10.3847/PSJ/aca4d1  

   Pan 潘, Jiaming 嘉明; Lin 林, Hsing Wen 省文; Gerdes, David W.; Napier, Kevin J.; Wang 王, Jichi 骥驰; Abbott, T. M. C.; Aguena, M.; Allam, S.; Alves, O.; Bacon, D.; et al (December 2022, The Planetary Science Journal)

   Abstract The Jupiter Trojans are a large group of asteroids that are coorbiting with Jupiter near its L4 and L5 Lagrange points. The study of Jupiter Trojans is crucial for testing different models of planet formation that are directly related to our understanding of solar system evolution. In this work, we select known Jupiter Trojans listed by the Minor Planet Center from the full six years data set (Y6) of the Dark Energy Survey (DES) to analyze their photometric properties. The DES data allow us to study Jupiter Trojans with a fainter magnitude limit than previous studies in a homogeneous survey withgrizband measurements. We extract a final catalog of 573 unique Jupiter Trojans. Our sample include 547 asteroids belonging to L5. This is one of the largest analyzed samples for this group. By comparing with the data reported by other surveys we found that the color distribution of L5 Trojans is similar to that of L4 Trojans. We find that L5 Trojans’g−iandg−rcolors become less red with fainter absolute magnitudes, a trend also seen in L4 Trojans. Both the L4 and L5 clouds consistently show such a color–size correlation over an absolute magnitude range 11 <H< 18. We also use DES colors to perform taxonomic classifications. C- and P-type asteroids outnumber D-type asteroids in the L5 Trojans DES sample, which have diameters in the 5–20 km range. This is consistent with the color–size correlation. 

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2. An ALMA Search for High-albedo Objects Among the Midsized Jupiter Trojan Population

   https://doi.org/10.3847/1538-3881/ac559e  

   Simpson, Anna M.; Brown, Michael E.; Schemel, Madeline J.; Butler, Bryan J. (June 2022, The Astronomical Journal)

   Abstract We use Atacama Large Millimeter Array (ALMA) measurements of 870μm thermal emission from a sample of midsized (15–40 km diameter) Jupiter Trojan asteroids to search for high-albedo objects in this population. We calculate the diameters and albedos of each object using a thermal model which also incorporates contemporaneous Zwicky Transient Facility photometry to accurately measure the absolute magnitude at the time of the ALMA observation. We find that while many albedos are lower than reported from WISE, several small Trojans have high albedos independently measured both from ALMA and from WISE. The number of these high-albedo objects is approximately consistent with expectations of the number of objects that recently have undergone large-scale impacts, suggesting that the interiors of freshly-crated Jupiter Trojans could contain high-albedo materials such as ices. 

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3. A Collision Mechanism for the Removal of Earth's Trojan Asteroids

   https://doi.org/10.3847/PSJ/ac6958  

   Napier, Kevin J.; Markwardt, Larissa; Adams, Fred C.; Gerdes, David W.; Wen Lin 林, Hsing 省文 (May 2022, The Planetary Science Journal)

   Abstract Due to their strong resonances with their host planet, Trojan asteroids can remain in stable orbits for billions of years. As a result, they are powerful probes for constraining the dynamical and chemical history of the solar system. Although we have detected thousands of Jupiter Trojans and dozens of Neptune Trojans, there are currently no known long-term stable Earth Trojans (ETs). Dynamical simulations show that the parameter space for stable ETs is substantial, so their apparent absence poses a mystery. This work uses a large ensemble ofN-body simulations to explore how the Trojan population dynamically responds if Earth suffers large collisions, such as those thought to have occurred to form the Moon and/or to have given Earth its late veneer. We show that such collisions can be highly disruptive to the primordial Trojan population, and could have eliminated it altogether. More specifically, if Earth acquired the final 1% of its mass through $\mathit{}\left(10\right)$collisions, then only ∼1% of the previously bound Trojan population would remain. 

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4. From Centaurs to Comets - 40 years

   https://doi.org/10.1016/B978-0-12-816490-7.00014-X  

   Peixinho, Nuno; Thirouin, Audrey; Tegler, Stephen C.; Di Sisto, Romina; Delsanti, Audrey; Guilbert-Lepoutre, Aurélie; Bauer, James G. (January 2020, Elsevier)

   Review chapter to be published in the book "The Transneptunian Solar System", Editors: Dina; doi:10.1016/B978-0-12-816490-7.00014-X (Ed.)

   In 1977, while Apple II and Atari computers were being sold, a tiny dot was observed in an inconvenient orbit. The minor body 1977 UB, to be named (2060) Chiron, with an orbit between Saturn and Uranus, became the first Centaur, a new class of minor bodies orbiting roughly between Jupiter and Neptune. The observed overabundance of short-period comets lead to the downfall of the Oort cloud as exclusive source of comets and to the rise of the need for a Trans-Neptunian comet belt. Centaurs were rapidly seen as the transition phase between Kuiper belt objects, also known as Trans-Neptunian objects (TNOs) and the Jupiter-family comets (JFCs). Since then, a lot more has been discovered about Centaurs: They can have cometary activity and outbursts, satellites, and even rings. Over the past four decades since the discovery of the first Centaur, rotation periods, surface colors, reflectivity spectra, and albedos have been measured and analyzed. However, despite such a large number of studies and complementary techniques, the Centaur population remains a mystery as they are in so many ways different from the TNOs and even more so from the JFCs. 

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5. A Gateway to Astronomical Image Processing: Vera C. RubinObservatory LSST Science Pipelines on AWS

   Bektesevic, Dino; Chiang, Hsin-Fang; Lim, Kian-Tat; Miller, Todd L.; Thain, Greg; Jenness, Tim; Bosch, James; Salnikov, Andrei; Connolly, Andrew (October 2020, Gateways 2020, Online)

   null (Ed.)

   The Legacy Survey of Space and Time, operated by the Vera C. Rubin Observatory, is a 10-year astronomical survey due to start operations in 2022 that will image half the sky every three nights. LSST will produce ~20TB of raw data per night which will be calibrated and analyzed in almost real-time. Given the volume of LSST data, the traditional subset-download-process paradigm of data reprocessing faces significant challenges. We describe here, the first steps towards a gateway for astronomical science that would enable astronomers to analyze images and catalogs at scale. In this first step, we focus on executing the Rubin LSST Science Pipelines, a collection of image and catalog processing algorithms, on Amazon Web Services (AWS). We describe our initial impressions of the performance, scalability, and cost of deploying such a system in the cloud. 

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