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The mass versus orbital distance of currently discovered and characterized exoplanets. Solar system planets are indicated as well. The hexagonal icons, indicating spectroscopic characterization studied done using JWST, are adopted from Espinoza & Perrin (2025). Direct imaging, currently limited to far out and large planets, will have to advance in sensitivity and contrast ratio to reach Earth-like planets. -- astro-ph.EP

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy

Spectral Signatures From The Habitable Zone

by Keith CowingApril 13, 2026April 13, 2026

This work describes the context and approach for the detection of spectroscopic signatures from planets in the habitable zone of nearby stars.

Geometries of the H-addition reactions on HNC leading to cis- and trans-HC•NH (reactions R4-cis and R4-trans). Distances are in Å -- astro-ph.GA

Astrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Icy Worlds, Imaging & Spectroscopy, Interstellar

Methanimine As A Sink In The HCN And HNC Solid State Hydrogenation Network

by Keith CowingApril 13, 2026April 13, 2026

Exoplanet detection limits from the neural network framework in the case of HARPS-N solar spectra. Left: Detection limit map in the period-amplitude domain. The red dots indicate the successful detection by the trained NN with a false alarm probability (FAP) > 0.1%. Middle: Amplitude comparison between the injected and recovered signals in the period-amplitude domain. The amplitude difference for most of the recovered signals are < 20%. The large difference at low amplitude (0.1 m/s) is likely due to noise in the data. Right: Phase comparison between the injected and recovered signals in the period-amplitude domain. The phase difference for most of the recovered planets is < 0.04. The large differences at long periods is likely due to a poorer sampling of the phase for long-period planetary signals.--astro-ph.EP

AI - Data - Apps - Cybernetics, Astrobiology (general), Astrochemistry, Astrogeology, Astronomy & Telescopes, Habitable Zones, Imaging & Spectroscopy

Machine Learning As A Transformative Tool for (Exo-)Planetary Science

by Keith CowingApril 13, 2026April 13, 2026

Schematic overview of the data-processing workflow in this work. After splitting the 2C data into three antenna spectra, we first conduct a general comb diagnostics for each antenna, then perform per-antenna PCA decomposition, basis alignment, and periodogram/FT/ACF analysis. The component-level results are finally combined to distinguish non-shared periodic signals from shared or comb-like RFI. -- astro-ph.IM

Artemis & Lunar Exploration, Astronomy & Telescopes, Biosignatures & Paleobiology, Missions & Hardware, Moon, SETI & Technosignatures

First Lunar Farside SETI Observations for Periodic Signals With The Low-frequency Radio Spectrometer Of Chang’E-4 Mission

by Keith CowingApril 12, 2026April 12, 2026

PSF-subtracted images of all targets. The observation subarray of each target is indicated. The first seven images are zoomed in to area of 11.0” × 11.0” for clearer view of the central regions. For the last three targets, the small size (4.4” × 4.4”) is due to the choice of the observation subarray. The location of the star PSF center is denoted by the white cross. Sources around LHS 1478, TOI-1468, and TOI-270 are labeled with letters, which are likely background sources. The arrow near HD 260655 indicates a low-S/N identification of possible close companion. We further examined this detection in Section 4.4. North is up and east is to the left. -- astro-ph.EP

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

A Search For Wide-orbit Planets Around M-dwarfs Using Deep MIRI 15-micron Images

by Keith CowingApril 12, 2026April 12, 2026

Plotted here are the Kepler confirmed planets/candidates with Gaia DR2 radius improvements. Selection criteria are main-sequence host-star with temperature 5000-6500 K and planet radius errors less than ±10%. Data source: exoplanet archive (Akeson et al. 2013) (Christiansen et al. 2025) (Thompson et al. 2017) and Gaia DR2 Berger et al. (2020, 2018); Brown et al. (2018); Lindegren et al. (2018). Sub-Panels: (1): 1100+ planets fulfilling the criteria, with gray ellipse showing the typical errors in planet radius and temperature. (2) and (3): Smooth Kernel fit to data. (4): All known transiting Hot Jupiters (Rp > 8 R⊕) which have masses measured from RV surveys (e.g. WASP, HAT, HAT-P, etc.), colored by metallicity ([Fe/H]). also c.f. (Castro-González et al. 2024). -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Stellar Cartography

Exoplanet Orbital Distribution Around FGK Sun-like Host Stars I: Planet Occurrence Rate Derived From The Kepler Mission And Theoretical Interpretations From Planet Formation

by Keith CowingApril 11, 2026April 11, 2026

Transmitted power vs wavelength to various star systems of potential interest. The red dashed line shows the current wavelength limit of reflective optics. -- Nature

Astronomy & Telescopes, Biosignatures & Paleobiology, Interstellar, SETI & Technosignatures

X-ray And γ-ray Beam Interstellar Communication And Implications For SETI

by Keith CowingApril 11, 2026April 11, 2026

EXOKYOTO4D -- Kyoto University

AI - Data - Apps - Cybernetics, Astronomy & Telescopes, Exoplanets, -moons, -comets

Release Of The Exoplanet Database “EXOKYOTO3D” And Announcement Of The Extended Version “EXOKYOTO4D”

by Keith CowingApril 10, 2026April 10, 2026

The final accumulated nighttime light change area: A night-time view of Earth, capturing human activity across the eastern hemisphere of the planet through the emissions of artificial light. Derived from satellite images taken daily over the past decade, the image maps the dynamics of the human night-time activity, with golden areas experiencing brightening, purple areas featuring dimming, and white areas experiencing both. Credit © Michala Garrison/NASA Earth Observatory

Astronomy & Telescopes, Imaging & Spectroscopy, SETI & Technosignatures

Terrestrial Technosignatures: Satellites Capture The Glowing Pulse Of Human Civilization

by Keith CowingApril 10, 2026April 10, 2026

Main plot: mass-radius plot of well-studied exoplanets from TepCat in between 1-20 Earth masses and 1-4 Earth radii. Some theoretical mass-radius curves are shown for comparison. Although a subset of planets is below the silicate (i.e. pure rock) curve and can be identified as rocky planets, a larger proportion of the planets is above this curve. In particular, they exhibit a clustering in the range of 6-10 Earth masses as shown by the background with 2D probability density contours and shading. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Stellar Cartography

Exoplanet Orbital Distribution Around FGK Sun-like Host Stars II: A Valley In The Orbital Semi-major Axis Distribution Of Sub-Neptunes

by Keith CowingApril 10, 2026April 10, 2026