astro-ph.EP] Archives

Boundaries of the Habitable Zone. The horizontal axis marks the radiative flux relative to Earth and the vertical ones, the effective temperature and approximate spectral type of the host star (spectral type boundaries are marked by horizontal thin dashed lines). Solid green curves indicate the conservative HZ boundaries for rapidly rotating planets. Also shown is the Recent Venus inner HZ boundary (green dashed) and the Greenhouse Runaway one (light green dashed curve). The blue dashed curves represent the inner extended HZ boundary for locked planets (Wandel 2025). A global heat transport of 30% (f=0.3) and albedo of 0.3 are assumed. The curve marked “Night ice evaporation” is the moist greenhouse curve shifted to the right by a factor of 1/0.3=3.3. The curves marked “Night Moist Greenhouse” and “Night Greenhouse runaway” are the moist and runaway greenhouse curves for f=0.3 (Wandel 2025). The red curve marks the tidal locking radius (Wandel 2023b) and blue dots denote Solar System planets. -- astro-ph.EP

Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Habitable Zones, Status Report

Exoplanets Beyond The Conservative Habitable Zone: II. Occurrence

by Keith CowingOctober 9, 2025

We demonstrate that the extension of the Habitable Zone (HZ) due to the presence of liquid water on the night side of tidally locked planets, modelled in this and earlier […]

Graph of the semimajor axis and eccentricity of the final terrestrial planets in the simulations of Table 1. Note that the majority of the planets formed or reached their final orbits in the range of 0.45 – 0.65 au. -- astro-ph.EP

Exoplanets, -moons, -comets, Status Report

Secular Resonances in Planet-Hosting Binary Stars. II. Application to Terrestrial Planet Formation

by Keith CowingOctober 8, 2025October 8, 2025

Continuing our study of the effects of secular resonances on the formation of terrestrial planets in moderately close binary stars, we present here the results of an extensive numerical simulations […]

Fraction of atmosphere retained 1 Gyr after a hypothetical Moonforming impact with 𝑓esc = 0.01 and 𝐷max = 100 km, as a function of the initial atmospheric mass (𝑚atm0). Filled circles represent an Earth-like, volatile-rich atmosphere with 𝜇 = 29, and the filled diamonds represent an atmosphere with a primordial (solar) composition with 𝜇 = 2.35. For completely depleted atmospheres (𝑚atm/𝑚atm0 < 10−4 ), the time of depletion (𝑡atm, lost) is indicated by the fill colors. Dotted lines connecting markers of the same 𝜇 values are included as visual guides. -- astro-ph.EP

Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Extinction events, Gaia - Planetary Perspectives, Habitable Zones, Impact events, Status Report

Re-accretion of Giant Impact Ejecta Can Drive Significant Atmospheric Erosion on Terrestrial Planets

by Keith CowingOctober 8, 2025October 8, 2025

Giant impacts, the collisions between planetary embryos, play a crucial role in sculpting the planets and their orbital architectures.

An average of the continuum-removed spectra of the leading and trailing hemispheres of Mimas and Tethys and the leading hemispheres of Dione and Rhea, in black, and of the trailing hemispheres of Dione and Rhea, in red. The lines at the bottom show measured wavelengths of CO2 in different states, including in pure crystalline form and trapped as clathrate in crystalline water ice (Oancea et al. 2012), trapped in amorphous ice (Sandford & Allamandola 1990; G´alvez et al. 2008) and physisorbed onto minerals (Hibbitts & Szanyi 2007), which can lead to a wide range of wavelengths. The shorter wavelength 4.2487 µm line associated with the darker hemispheres of Dione and Rhea appears to have no corresponding absorption in the 2.7 µm region. -- astro-ph.EP

Dione, Enceladus, Hyperion, Iapetus, Icy Worlds, Mimas, Phoebe, Rhea, Saturn, Status Report, Tethys

A JWST Study Of CO2 On The Satellites Of Saturn

by Keith CowingOctober 6, 2025October 6, 2025

Solid state CO2 has been detected throughout the outer solar system, even at temperatures where crystalline CO2 is unstable, requiring that the CO2 be trapped in a separate host material.

Continuum-subtracted spectra of comet 3I obtained on August 28 and September 3+4. Three narrow FeI lines are detected on August 28 in this spectral range, FeI λ3719.93Å being the brightest iron line detected in our spectra. On the average spectrum obtained in September 3+4 (shifted vertically for clarity), the FeI lines are brighter, and four of them are detected. Broad emission features due to background [OII] emission at 3727Å and 3729Å are also observed. -- astro-ph.EP

Astrochemistry, Astrogeology, Astronomy & Telescopes, Comets and Asteroids, Imaging & Spectroscopy, Interstellar, Status Report

Extreme NiI/FeI Abundance Ratio In The Coma Of The Interstellar Comet 3I/ATLAS

by Keith CowingOctober 2, 2025October 2, 2025

Emission lines of FeI and NiI are commonly found in the coma of solar system comets, even at large heliocentric distances.

Signal amplitudes in the vicinity of the putative exomoon around β Pic b suggested by Poon et al. (2024) as a function of moon mass and semi-major axis for RV studies on the left and astrometric searches on the right. The grey shaded region is the parameter space where a P24- moon is likely to reside if it is indeed real. The dashed lines indicate contours delineating the provided signal strengths. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Habitable Zones, Status Report

Astrometric Exomoon Detection By Means Of Optical Interferometry

by Keith CowingSeptember 27, 2025September 27, 2025

Context: With no conclusive detection to date, the search for exomoons, satellites of planets orbiting other stars, remains a formidable challenge. Detecting these objects, compiling a population-level sample and constraining […]

Local view of the simulated innermost disk flux distribution models of ϵ Eri. Left Panel: Low inclination disk model. Middle Panel: High inclination disk model. Right Panel: Continuous disk model. The outer line represents planetary trace based on orbital parameters from (Thompson et al., 2025). --astro-ph.EP

Astronomy & Telescopes, Biogeochemical Cycles & Geobiology, Epsilon Eridani, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Direct Imaging For The Debris Disk Around epsilon Eridani With The Cool-Planet Imaging Coronagraph

by Keith CowingSeptember 23, 2025September 23, 2025

We analyze the inner debris disk around ϵ Eridani using simulated observations with the Cool-Planet Imaging Coronagraph (CPI-C).

Filamentary structures and anisotropy are observed across the dynamic range of star formation. Starting at the star-forming scale, (1) shows the OMC-1 star-forming filament observed by ALMA+IRAM 30 m in the form of ‘fibers’ identified as velocity coherent on 30,000 au scales (Hacar et al., 2018). Such filamentary behavior and anisotropy is associated with the presence of (2) dense protostellar cores, as in the heterogeneous column density of L1709, inferred from Herschel observations (Arzoumanian et al., 2019) and fit with ballistic free-fall trajectories as in the case of (3) the 10,500 au ‘streamer’ structure around the protostar Per-Emb 2 seen in HC3N by ALMA (Pineda et al., 2020). The structured infalling envelopes of cores like L1709 can be associated with the presence of substructure in the (4) thermal dust continuum (1.3mm) emission from ALMA of its young planet-forming disk (< 500 kyr old) IRS-63 (Segura-Cox et al., 2020) -- astro-ph.EP

Astrochemistry, Astrogeology, Exoplanets, -moons, -comets, Meteorites & Asteroids, Planetary Protection & Biosafety, Status Report

Infall And Disk Processes – The Message From Meteorites

by Keith CowingSeptember 21, 2025September 21, 2025

How do planetary systems, in general, and our own Solar System (SS), in particular, form? In conjunction, Astronomy and Isotope Cosmochemistry provide us with powerful tools to answer this age-old […]

White-light TRAPPIST-1 e JWST/NIRSpec PRISM transit light curves. (Top) Datapoints of the transit event (grey; binned at a cadence of 14-seconds) along with the best-fit transit plus systematics model (black; which includes a visit-long slope and a GP; see text for details). The date at which each observation was obtained is indicated at the top of each panel. (Middle) Residuals of the data minus the best-fit light curve model in parts-per-million (ppm); the root-mean-square of the data at this 14-second cadence is indicated for each observation. (Bottom) Light curves at the Hα line (0.656±0.02 µm, in parts per thousand; ppt) at the same cadence as the white-light curves (pale blue points), and binned at 5-minutes (solid blue points); note how a flare is revealed at about −0.25 hr in this light curve as the most likely explanation for the bump in the July 23, 2023 transit event. -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Habitable Zones, Imaging & Spectroscopy, Status Report, TRAPPIST-1, Water/Hycean Worlds & Oceanography

JWST-TST DREAMS: NIRSpec/PRISM Transmission Spectroscopy of the Habitable Zone Planet TRAPPIST-1 e

by Keith CowingSeptember 9, 2025September 9, 2025

TRAPPIST-1 e is one of the very few rocky exoplanets that is both amenable to atmospheric characterization and that resides in the habitable zone of its star — located at […]

D/H ratio in Solar System objects. Comets exhibit large variations between 1 and 3 times Vienna Standard Mean Ocean Water (VSMOW). The red diamond and arrow mark the revised value of 2.59 ± 0.36 × 10−4 in comet 67P/C-G.2 -- astro-ph.EP

Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Comets and Asteroids, Habitable Zones, Icy Worlds, Impact events, Status Report, Water/Hycean Worlds & Oceanography

Isotopic Composition Of Cometary Water And The Origin Of Earth’s Oceans

by Keith CowingSeptember 3, 2025September 3, 2025

Studies of the water content and isotopic composition of water-rich asteroids and comets are of key interest for understanding the late accretion stage of the Solar System cometary and chondritic […]

astro-ph.EP]

Exoplanets Beyond The Conservative Habitable Zone: II. Occurrence

Secular Resonances in Planet-Hosting Binary Stars. II. Application to Terrestrial Planet Formation

Re-accretion of Giant Impact Ejecta Can Drive Significant Atmospheric Erosion on Terrestrial Planets

A JWST Study Of CO2 On The Satellites Of Saturn

Extreme NiI/FeI Abundance Ratio In The Coma Of The Interstellar Comet 3I/ATLAS

Astrometric Exomoon Detection By Means Of Optical Interferometry

Direct Imaging For The Debris Disk Around epsilon Eridani With The Cool-Planet Imaging Coronagraph

Infall And Disk Processes – The Message From Meteorites

JWST-TST DREAMS: NIRSpec/PRISM Transmission Spectroscopy of the Habitable Zone Planet TRAPPIST-1 e

Isotopic Composition Of Cometary Water And The Origin Of Earth’s Oceans

NASA Spaceline Current Awareness List #1,206 2 July 2026 (Space Life Science Research Results)

Older Than The Sun: Astronomers Find New Clues To The Origin Of Interstellar Comet 3I/ATLAS

Carl Sagan Month: Call For Participation

The Habitable Worlds Observatory Technology Development Plan

Searching For The Elusive CH2+ With The James Webb Space Telescope. Another Carbocation To Constrain Astrochemical Networks