Astrochemistry

[astro-ph.GA] Sulfur (S) chemistry in the interstellar medium remains poorly constrained due to the longstanding “missing sulfur” problem, where a significant fraction of cosmic sulfur in molecular clouds remains unidentified.

Initial 𝑎c–𝑒c distribution of the 32,000 comets used in each end-to-end calculation. Dashed lines mark the semimajor axes of P7 and P8. The circular and eccentric planet calculations use identical comet initial states.-- [astro-ph.EP]

Comets and Asteroids

Planetary Eccentricity Enhances Inward Comet Transport But Suppresses Gentle Impacts

[astro-ph.EP] Comets can supply volatile and prebiotic material to rocky planets, but survival of fragile molecules depends on atmospheric entry and impact. Compact planet chains can transfer comets inward at […]

Illustration of the different size averages for Renazzo (after the data of Ebel et al. (2024)) on a back-scattered electron image of polished section 719sp3 of the Muséum national d’Histoire naturelle collection (Jacquet et al., 2012).-- [astro-ph.EP]

Astrogeology

Chondrule Size Averaging In Two And Three Dimensions

[astro-ph.EP] Chondrule sizes are an important discriminant of chondrite groups and chondrule formation theories. Yet most studies report 2D sizes without attempting the somewhat tedious corrections to 3D proposed in […]

The per-tile processing chain, applied to the Detector-4 tile of Fig. 1. (a) After flag masking and zodiacal-light subtraction, the input to the stellar subtraction. (b) After fitting and subtracting the empirical PSF at every catalogued source above the magnitude limit, with the saturated cores of the brightest stars masked. (c) After the median filter and the Gaussian smoothing to 2.6 ′ , which is what is coadded into the HEALPix maps. All three panels share a single histogram-equalised colour scale. -- [astro-ph.GA]

A Full-Sky SPHEREx Map of Integrated 3.3 And 3.4 μm PAH Emission

[astro-ph.GA] Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the interstellar medium and are among its smallest carbonaceous grains.

Final semi-major axes and masses for all objects produced in simulations with regular disks. The left panel shows objects produced in disks with low C/O ratios and the right one shows planets in high C/O ratio disks. The dash-dotted line shows the initial mass of planestesimals in our simulations while the dotted line shows the initial mass of planetary embryos. We consider planets to be anything at or above the initial embryo mass, fragments to be anything below the initial planetesimal mass, and planetesimals to be any object at or above the initial planetesimal mass but below the initial embryo mass. -- [astro-ph.EP]

Exoplanets, -moons, -comets

Correlations Between The Carbon-to-Oxygen Ratio and the Orbital and Physical Properties of Exoplanets

[astro-ph.EP] Studies suggest that protoplanetary disks around stars with high carbon-to-oxygen (C/O) ratios can produce terrestrial planets with carbon-dominated compositions instead of silicon-dominated ones.

Median protoplanetary disk composition predicted by the chemical model at different metallicities [Fe/H]. LEFT: Median overall composition. RIGHT: Median refractory composition. -- [astro-ph.EP]

Interstellar

On The Compositions Of Interstellar Objects

[astro-ph.EP] As physical samples of distant planetary systems, the compositions of interstellar objects (ISOs) should correlate with the properties of their diverse parent stars.

Chemical clock relations for planet-hosting solar analogs, showing abundance ratios as a function of stellar age for [Y/Mg], [Y/Al], [Ba/Mg], [Ba/Al], [Sr/Mg], and [Y/(Mg+Al)/2]. Data points are color-coded by metallicity ([Fe/H]). Black lines show best-fit linear relations derived using Deming regression, accounting for uncertainties in both variables, and shaded regions indicate 1σ confidence intervals. All abundance ratios show statistically significant correlations with stellar age. -- [astro-ph.EP]

Exoplanets, -moons, -comets

Planets Around Solar Twins/Analogs (PASTA) III: Chemical Clock Relations in Planet-Hosting Solar Analogs

[astro-ph.EP] Context. Abundance ratios between elements synthesized on different nucleosynthetic timescales provide empirical chemical clocks for estimating stellar ages, but robust calibrations require homogeneous samples with precise stellar parameters and […]

Infrared spectra of pure H2S (blue) and H2O:H2S (10:1) (red) ice mixtures after UV irradiation followed by warm-up to room temperature, measured at 300 K. The residue from the H2S ice does not show any IR absorption band. Functional groups assigned to bands in the H2O:H2S (10:1) residue are indicated at the top; vibrational bands and assignments are also listed in Table 1, along with possible carrier species or chemical families producing those features. -- [astro-ph.GA]

Water Enhances The Formation Of Refractory Sulfur In Interstellar Ices

[astro-ph.GA] Sulfur is the tenth most abundant element in space, yet it is strongly depleted in the gas phase of dense interstellar regions, suggesting sequestration in dust grain components that […]

Rogelio Bernal Andreo - https://en.wikipedia.org/wiki/Orion_molecular_cloud_complex#/media/File:Orion_Head_to_Toe.jpg The photograph appeared as the Astronomy Picture of the Day on October 23, 2010.- wikipedia

Chemical Diversity Of Dense Cores In Orion B: The Role Of The Environment

by Keith CowingOctober 3, 2026October 3, 2026

[Astronomy & Astrophysics] Context. Pre-stellar cores are the sites of the earliest stages of star formation. Dust continuum observations are often used to identify and characterise their properties yet only […]

Rest-frame equivalent widths of C iii] 𝜆𝜆1907, 1909 (left) and C iv 𝜆𝜆1548, 1550 (right) against the direct 𝑇e-based ([O III]𝜆4363) metallicity. Curves are the star-forming photoionisation grids of Nakajima et al. (2018) at a burst age of 1 Myr and log(𝑛H/cm−3 ) = 3. Solid curves represent the POPSTAR single-star models (Mollá et al. 2009), and dashed curves indicate the BPASS binary models (Eldridge et al. 2017), coloured by ionisation parameter as shown in the colour-bar. -- [astro-ph.GA]