astro-ph.EP Archives

Spectral characterization of Chiron’s surface composition. a Comparison of the bestfit spectral model of the surface composition (red) with the measured spectrum (black). The surface is best described by an intimate mixture of water ice in both amorphous and crystalline phases, carbon dioxide ice, and tholin-like materials. b Residuals between the model and the data show an excellent fit, with a root mean square deviation that is just 1% higher than the average scatter in the data. c Zoomed-in view of the complex organic absorption feature spanning 3.3–3.6 µm, with the individual component bands indicated by dashed lines. Comparison between the measured spectrum and synthetic spectra of several candidate species, convolved to the spectral resolution of the data, points to C3H8 and/or ice tholins produced by the irradiation of H2O ice and C2H6 as the most plausible candidates for the observed organic feature. -- astro-ph.EP

Astrochemistry, Astrogeology, Biochemistry & Organic Chemistry, Comets and Asteroids, Icy Worlds, Imaging & Spectroscopy, Status Report

JWST Reveals Anomalously Enhanced Methane Outgassing From Below Chiron’s Water Ice And Carbon Dioxide Bearing Surface

by Keith CowingMay 26, 2026May 26, 2026

Centaurs are inward-scattered Kuiper belt objects, with some exhibiting comet-like activity. The physical mechanisms powering this activity remain poorly understood, with carbon monoxide (CO) sublimation or the crystallization of amorphous […]

A northern polar projection of Jupiter indicating the latitude and longitude ranges adopted for coaddition of individual spectra. The circumference latitude is 40◦ (planetocentric), enclosed concentric circles are spaced by 4◦ in latitude. The magenta line represents the statistical mean position of the auroral oval (Bonfond et al., 2017). Spatial bins in black represent regions that do not overlap in latitude with the auroral oval, blue and red spatial bins represents areas outside and inside the auroral oval, respectively. TEXES achieves diffraction-limited spatial resolutions of 0.7” to 1.4” over the wavelength range adopted in this study, which corresponds to a latitude-longitude footprint of 5-10◦ at 60◦N. -- astro-ph.EP

Astrochemistry, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Gas Giants, Imaging & Spectroscopy, Jupiter, Status Report

Detection Of Propadiene (CH2CCH2), Propene (C3H6) And Non-detection Of Propane (C3H8) In Jupiter’s Northern Polar Stratosphere

by Keith CowingMay 25, 2026May 25, 2026

We report the first detection of stratospheric propadiene (CH2CCH2) and propene (C3H6) at Jupiter’s mid-to-high northern latitudes using IRTF-TEXES measurements recorded on March 5-6, 2025.

Upper panels: Equatorial rotational velocity (veq) vs. projected rotational velocity (v sin i) for stars in Tiers 1, 2, and 3. The v sin i values are taken directly from the ARC and the veq values are calculated using Prot from the ARC and R⋆ from the HPIC. Several stars in each tier fall in a region of parameter space that is mathematically forbidden, i.e., requiring sin i > 1. Lower Panels: Expected and observed inclination distributions for stars in Tiers 1, 2, and 3. The observed distributions are systematically distinct from the expected distributions. Not only do they predict undefined stellar inclinations, but the results favor face-on orbits (i = 0◦ ) rather than edge-on orbits (i = 90◦) as one would expect if stellar spin axes were drawn from an isotropic distribution. -- astro-ph.SR

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report

HWO Target Stars and Systems: Activity and Rotation Catalog (ARC) of Potential Target Stars for the Habitable Worlds Observatory

by Keith CowingMay 24, 2026May 24, 2026

A major goal of the Habitable Worlds Observatory (HWO) is to precisely characterize exoplanets and their atmospheres.

ExoCAM simulations of Earth from the present up to 2.0 Gyr in the future, assuming CO2 remains fixed at 400 ppm. The top row shows surface temperature, the middle row shows precipitation minus evaporation, and the bottom row shows the habitability metric developed by Woodward et al. (2025) (Eqs. (D1) and (D2)). All quantities are 20-year averages after the model has reached a steady-state. Increases in temperature due to a brightening sun cause an increase in habitability up to 1.5 Gyr due to the greening of the poles, but habitability decreases significantly by 2.0 Gyr as Earth becomes too hot for complex vegetative life. This corresponds to a weak temperature dependence of weathering, in which Earth’s CO2 levels do not change even as the climate warms (c.f., Graham et al., 2024). -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Desert Worlds, Gaia - Planetary Perspectives, Imaging & Spectroscopy, Space Agriculture, Status Report, Terraforming & Geoengineering, Water/Hycean Worlds & Oceanography

Maximum Lifetime Of The Vegetative Biosphere

by Keith CowingMay 23, 2026May 23, 2026

We use a three-dimensional model to calculate steady-state climates at various intervals in Earth’s future, across a parameter space of increasing insolation and decreasing CO2 mixing ratio.

A demonstration of the limitations of the PSPT data processing pipeline, which did not process the limb uniformly with the rest of the Solar disc. The solid blue line is the stated extent of the solar disk in the original dataset, and the dashed red line is the extent to which the data has been cleaned. Note between the red and blue lines there exists a slight intensity increase — an example of the difference between the processed and unprocessed data separated by this boundary. -- astro-ph.SR

Astronomy & Telescopes, Imaging & Spectroscopy, Space Weather & Heliophysics, Status Report, Stellar Cartography

Astrometric Exoplanet Detection Survives Solar-like Stellar Contamination

by Keith CowingMay 23, 2026May 23, 2026

Astrometric monitoring of stars provides a promising method for discovery of low-mass planets around nearby Sun-like stars.

Protoplanetary disk images (top row) and scattered-/transmitted-light spectra (bottom-left and bottom-middle) obtained from the radiative-transfer simulations, together with the crystallinity dependence of their Fresnel-feature heights (bottom-right). For the edge-on case, the Fresnel-feature height is measured in absolute value of feature depth. Alt text: Theoretical images, spectra, and Fresnel feature height of the protoplanetary disks. -- astro-ph.EP

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Imaging & Spectroscopy, Interstellar, Status Report

Constraints On The Crystallinity Of Water Ice In Planet-forming Disks From Infrared Scattered-Light Spectra

by Keith CowingMay 23, 2026May 23, 2026

The crystallinity of water ice not only records the thermal history experienced by an astronomical body, but also affects the composition of forming planets by controlling the trapping of volatile […]

(Top) A simulated transit depth spectrum showing SF6 and NF3 in the atmosphere of terrestrial exoplanets of different atmospheric compositions orbiting an M Dwarf star. The concentrations of SF6 and NF3 are at 1 ppm. (Bottom) Absorption cross sections for various atmospheric molecules, including the industrial produced SF6 and NF3. It is noted that concentrations of 1 ppm for both SF6 and NF3 are orders of magnitude above that of present-day Earth’s abundances of these two industrial gases. The high concentrations of SF6 and NF3 could exist in so-called “service worlds”. Figure from (Seager et al. 2023). -- astro-ph.EP

Astronomy & Telescopes, Biosignatures & Paleobiology, Imaging & Spectroscopy, Interstellar, SETI & Technosignatures, Status Report

The Search For Technosignatures: A Review Of Possibilities

by Keith CowingMay 22, 2026May 22, 2026

This paper aims to review the diverse range of technosignatures that have been proposed in the literature.

Phase folded best-fit transit models of TOI-4311b( purple) and TOI-4311c (green) with the underlying TESS (left) and CHEOPS (right) data in black in the top panel. The residuals are shown in the bottom. The data is binned into 30min showed by the white point. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

An Ultra-Short Period Super-Earth And A Sub-Neptune Orbiting The K Dwarf TOI-4311

by Keith CowingMay 22, 2026May 22, 2026

We report the discovery and characterisation of the multi-planetary system around TOI-4311, a K dwarf kinematically between the Galactic thick disk and Hercules stream. TOI-4311 hosts an ultra-short-period super-Earth (P∼0.99 […]

Declination of the 50 targets presenting the largest RSM′ values as a function of their respective score.

Astrochemistry, Astrogeology, Astronomy & Telescopes, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Spinning Out Of Focus: The Challenge Of Rotational Line Broadening In Exoplanet Reflection Spectroscopy

by Keith CowingMay 22, 2026May 22, 2026

Detecting light reflected off the dayside of an exoplanet in high-resolution spectroscopic data has proved to be a notoriously difficult endeavour. Despite several attempts, the faint signal has yet to […]

HR diagram track of the default case (final mass of 2.2 MJ ; see Table 1), showing its surface temperature (Eqs. 12, 19 or 21, depending on the phase) and total luminosity (Eq. 6). Highlighted key moments show the start point (•), detachment (⋆), the point of maximum luminosity (▼), disk dispersal (■), and the age of Jupiter (+). Table 2 lists the corresponding values for time, mass and radius. In the ascending branch small black triangles (▲) show linearly spaced time indicators every Myr. The black dots (•) represent post-detachment intervals equally spaced in log(time). Grey reference lines show two trends: the predicted slope derived in Sect. A, evaluated with the median late-attached-phase surface density of Σpla = 1.7 g cm−2 (labelled with L ∝ T 8 ), and a constant-radius track for Rp = 1 RJ , which approximates a cooling planet in the evolutionary phase before stellar irradiation becomes relevant (last downturn). -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report, Stellar Cartography

Planetary Formation Tracks On The Hertzsprung-Russell Diagram: Visualising The Processes Of Giant Planet Growth

by Keith CowingMay 21, 2026May 21, 2026

The Hertzsprung-Russell diagram (HRD) is central to stellar astrophysics but has rarely been used to interpret planet formation.

astro-ph.EP

JWST Reveals Anomalously Enhanced Methane Outgassing From Below Chiron’s Water Ice And Carbon Dioxide Bearing Surface

Detection Of Propadiene (CH2CCH2), Propene (C3H6) And Non-detection Of Propane (C3H8) In Jupiter’s Northern Polar Stratosphere

HWO Target Stars and Systems: Activity and Rotation Catalog (ARC) of Potential Target Stars for the Habitable Worlds Observatory

Maximum Lifetime Of The Vegetative Biosphere

Astrometric Exoplanet Detection Survives Solar-like Stellar Contamination

Constraints On The Crystallinity Of Water Ice In Planet-forming Disks From Infrared Scattered-Light Spectra

The Search For Technosignatures: A Review Of Possibilities

An Ultra-Short Period Super-Earth And A Sub-Neptune Orbiting The K Dwarf TOI-4311

Spinning Out Of Focus: The Challenge Of Rotational Line Broadening In Exoplanet Reflection Spectroscopy

Planetary Formation Tracks On The Hertzsprung-Russell Diagram: Visualising The Processes Of Giant Planet Growth

Astrobiologist Dale Andersen’s Antarctic Field Report: 9 November 2026: Lake Untersee Basecamp Update

Astrochemistry: Hubble and JWST Observe Star Formation in The Carina Nebula

Mapping the Historical Roots of Astrobiology: A Reference Publication Year Spectroscopy (RPYS) Analysis

The Agentic Observer Hackathon: Autonomous Decision-making in Simulated Astronomical Surveys

Tracking The Evolution of sub-Neptunes. I. Gyrochronology of Planet Hosting Stars