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1. Interstellar objects

   https://doi.org/10.1080/00107514.2023.2203976  

   Seligman, Darryl Z; Moro-Martín, Amaya (July 2022, Contemporary Physics)
2. The Interstellar Interlopers

   https://doi.org/10.1146/annurev-astro-071221-054221  

   Jewitt, David; Seligman, Darryl Z. (August 2023, Annual Review of Astronomy and Astrophysics)

   Interstellar interlopers are bodies formed outside of the Solar System but observed passing through it. The first two identified interlopers, 1I/‘Oumuamua and 2I/Borisov, exhibited unexpectedly different physical properties. 1I/‘Oumuamua appeared unresolved and asteroid-like, whereas 2I/Borisov was a more comet-like source of both gas and dust. Both objects moved under the action of nongravitational acceleration. These interlopers and their divergent properties provide our only window so far onto an enormous and previously unknown galactic population. The number density of such objects is ∼0.1 AU⁻³which, if uniform across the galactic disk, would imply 10²⁵to 10²⁶similar objects in the Milky Way. The interlopers likely formed in, and were ejected from, the protoplanetary disks of young stars. However, we currently possess too little data to firmly reject other explanations. ▪ 1I/‘Oumuamua and 2I/Borisov are both gravitationally unbound, subkilometer bodies showing nongravitational acceleration. ▪ The acceleration of 1I/‘Oumuamua in the absence of measurable mass loss requires either a strained explanation in terms of recoil from sublimating supervolatiles or the action of radiation pressure on a nucleus with an ultralow mass column density, ∼1 kg m⁻². ▪ 2I/Borisov is a strong source of CO and H₂O, which together account for its activity and nongravitational acceleration. ▪ The interlopers are most likely planetesimals from the protoplanetary disks of other stars, ejected by gravitational scattering from planets. 1I/‘Oumuamua and 2I/Borisov have dynamical ages ∼10⁸and ∼10⁹years, respectively. ▪ Forthcoming observatories should detect interstellar interlopers every year, which will provide a rapid boost to our knowledge of the population. 

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3. Machine Learning of Interstellar Chemical Inventories

   https://doi.org/10.3847/2041-8213/ac194b  

   Lee, Kin Long; Patterson, Jacqueline; Burkhardt, Andrew M.; Vankayalapati, Vivek; McCarthy, Michael C.; McGuire, Brett A. (August 2021, The Astrophysical Journal Letters)
4. Chemical models of interstellar cyanomethanimine isomers

   https://doi.org/10.1093/mnras/staa1979  

   Zhang, Xia; Quan, Donghui; Chang, Qiang; Herbst, Eric; Esimbek, Jarken; Webb, Matthew (September 2020, Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT The E-isomer of cyanomethanimine (HNCHCN) was first identified in Sagittarius B2(N) (Sgr B2(N)) by a comparison of the publicly available Green Bank Telescope (GBT) PRIMOS survey with laboratory rotational spectra. Recently, Z-cyanomethanimine was detected in the quiescent molecular cloud G+0.693−0.027 with the IRAM 30-m telescope. Cyanomethanimine is a chemical intermediate in the proposed synthetic routes of adenine, and may play an important role in forming biological molecules in the interstellar medium. Here we present a new modelling study of cyanomethanimine, using the nautilus gas–grain reaction network and code with the addition of over 400 chemical reactions of the three cyanomethanimine isomers and related species. We apply cold isothermal core, hot core, and C-type shock models to simulate the complicated and heterogeneous physical environment in and in front of Sgr B2(N), and in G+0.693−0.027. We identify the major formation and destruction routes of cyanomethanimine, and find that the calculated abundances of the cyanomethanimine isomers and the ratio of Z-isomer to E-isomer are both in reasonable agreement with observations for selected environments. In particular, we conclude that these isomers are most likely formed within or near the hot core without the impact of shocks, or in the cold regions with shocks. 

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5. Magnetic Misalignment of Interstellar Dust Filaments

   https://doi.org/10.3847/1538-4357/acb0c4  

   Cukierman, Ari J.; Clark, S. E.; Halal, George (April 2023, The Astrophysical Journal)

   Abstract We present evidence for scale-independent misalignment of interstellar dust filaments and magnetic fields. We estimate the misalignment by comparing millimeter-wave dust-polarization measurements from Planck with filamentary structures identified in neutral-hydrogen (Hi) measurements from Hi4PI. We find that the misalignment angle displays a scale independence (harmonic coherence) for features larger than the Hi4PI beamwidth (16.′2). We additionally find a spatial coherence on angular scales of $\mathit{}(1°)$. We present several misalignment estimators formed from the auto- and cross-spectra of dust-polarization and Hi-based maps, and we also introduce a map-space estimator. Applied to large regions of the high-Galactic-latitude sky, we find a global misalignment angle of ∼2°, which is robust to a variety of masking choices. By dividing the sky into small regions, we show that the misalignment angle correlates with the parity-violatingTBcross-spectrum measured in the Planck dust maps. The misalignment paradigm also predicts a dustEBsignal, which is of relevance in the search for cosmic birefringence but as yet undetected; the measurements ofEBare noisier than those ofTB, and our correlations ofEBwith misalignment angle are found to be weaker and less robust to masking choices. We also introduce an Hi-based dust-polarization template constructed from the Hessian matrix of the Hiintensity, which is found to correlate more strongly than previous templates with Planck dustBmodes. 

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