Earth-like Planet Archives - Astrobiology

[LEFT]: Schematic of the star–planet–observer geometry defining the phase angle α, measured between the star–planet and planet–observer directions. The hemisphere of the planet facing the star is fully illuminated (gold) at all times, while the opposite hemisphere remains in shadow. The observer sees only the portion of the illuminated hemisphere that is visible at a given α, with full illumination visible only at α = 0◦. [RIGHT]: Illustration of planetary phases along an edge-on orbit, with the star at the center and the observer direction indicated below the orbit. Although the star-facing hemisphere remains illuminated throughout the orbit, the visible fraction of this hemisphere changes with phase angle. Full phase occurs at α = 0◦, quadrature at α = 90◦, and new phase at α = 180 , with gibbous and crescent phases spanning the intermediate ranges. -- [astro-ph.EP]

Astronomy & Telescopes

The Impact of Planetary Phase Functions On Exo-Earth Detectability With EXOSIMS

by Keith CowingAugust 6, 2026August 7, 2026

[astro-ph.EP] The under-development NASA Habitable Worlds Observatory (HWO) aims to provide breakthroughs in exoplanet science, yet the most effective approaches to modeling the detection and characterization of potentially Earth-like worlds […]

NASA Exoplanet Archive -- NASA

Habitable Zones

Quantifying Detection Bias And Recovering Habitable Zone Occurrence Rates In The NASA Exoplanet Archive

by Keith CowingAugust 6, 2026August 6, 2026

[Astronomy and Computing] Transit surveys tend to underestimate how often habitable zone (HZ) planets appear. The core reason is geometric: the chance that an Earth-like planet transits a sun-like star […]

Overview of the simulation pipeline components used in this work. The modeling begins with hwo pol, a Poke front-end we constructed tailored to modeling the EACs. The ray trace file and coating data are fed to Poke which computes the Jones pupils and saves them as a FITS file. These data are loaded into hwo sim and applied on top of the phase and amplitude errors encountered by propagating through the OTA and tertiary collimator assembly (TCA, mirrors 3-5). The now polarization aberrated field is propagated through a scalar diffraction model, subject to jacobianfree wavefront control with perfect knowledge of the electric field. Using this control simulation, we can save a series of intensity images into a Yield Input Package, which is sent to the FRIDAY AYO calculator to close the loop to exoEarth yields. -- astro-ph.EP

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

Connecting Polarization To Exoplanet Yield Calculations For Habitable Worlds Observatory (HWO)

by Keith CowingJune 13, 2026June 13, 2026

The Habitable Worlds Observatory (HWO) aims to enable the detection and characterization of Earth-like planets around Sun-like stars to search for possible signs of life elsewhere in our universe.

Schematic summary of the surface temperature response to increasing pN2 on the pCO2 –pN2 plane, comparing Goldblatt et al. (2009, G+09), Wordsworth & Pierrehumbert (2013, WP13), and this work. For Goldblatt et al. (2009), the pink shaded region denotes the parameter range they explored, within which all cases show warming as pN2 increases. For Wordsworth & Pierrehumbert (2013), circles mark the parameter sets shown in their Figure 14a, and the annotation at the top summarizes their reported response. Circle size and color qualitatively indicate the surface temperature, with larger circles and warmer colors corresponding to higher temperatures. In Wordsworth & Pierrehumbert (2013), the sign of the response is inferred from the two data points connected by arrows, which indicate the direction of increasing pN2 . Background shading shows the approximate regimes obtained in this work, namely cooling, warming, and neutral surface-temperature response to increasing pN2. -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Gaia - Planetary Perspectives, Habitable Zones, Imaging & Spectroscopy, Status Report

Revisiting the Greenhouse Effect of Non-greenhouse Gases in the Atmospheres of Earth-like Planets

by Keith CowingMay 13, 2026May 13, 2026

Although non-greenhouse gases can vary substantially in abundance in Earth-like atmospheres, their climatic influences remain insufficiently understood.

The picture was taken from the top of the LSS after the chamber was reopened. It gives us a direct view of Plato’s 26 ultrasensitive cameras. These are the special eyes that the mission will use to monitor more than 150 000 bright stars at the same time, hunting for terrestrial planets orbiting Sun-like stars. -- ESA Larger image

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, PLATO, Press Release

Astrobiology Mission Update: Plato Habitable Exoplanet Hunter Integration

by Keith CowingApril 27, 2026April 27, 2026

The European Space Agency Plato mission has successfully completed a series of tough tests under space‑like conditions. With this accomplishment, the spacecraft is on track to lift off in early […]

Fitting of exoplanets. (a) The target star is HD 88230, with a hypothetical Earth-like planet placed at a distance of 1 AU from the star. (b) The target star is again HD 88230, with a hypothetical warm Jupiter placed at a distance of 0.1 AU. (c) The target star is HD 147513, which is known to host the detected Jovian planet HD 147513 b. The angular distance measurement accuracy is 1 µas. The black points represent the simulated planetary parameters, while the red points show the residuals after removing proper motion and parallax through fitting. The blue points depict the stellar motion orbit induced by planetary perturbations, derived from a Keplerian fit to the residuals. -- astro-ph.EP

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

Closeby Habitable Exoplanet Survey (CHES). V. Planetary Parameters Derived from Angular Separation Variations

by Keith CowingApril 1, 2026April 1, 2026

The Closeby Habitable Exoplanet Survey (CHES) aims to achieve microarcsecond-level astrometry of about one hundred nearby FGK-type stars within 10 parsecs to detect Earth-like planets.

Analog Studies, Astronomy & Telescopes, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Press Release

Identifying Surface Degeneracies in Single-Visit Reflected Light Observations of Modern Earth using the Habitable Worlds Observatory

by Keith CowingMarch 31, 2026March 31, 2026

Characterizing the surface and atmosphere of Earth-like planets in reflected light is a key goal for upcoming direct imaging surveys.

Ventilation of the ocean interior improves with slowing rotation.-- Science via PubMed

Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Gaia - Planetary Perspectives, Habitable Zones, Status Report, Water/Hycean Worlds & Oceanography

Slowing Planetary Rotation Influences Ocean Nutrient Cycling And Oxygenation

by Keith CowingFebruary 7, 2026

Marine habitability for complex life on Earth and Earth-like planets requires bioavailable nutrients and dissolved oxygen. The cycling of nutrients and oxygen is controlled by physical ocean circulation.

Cartoon illustration of the hybrid models. The difference between HM-U and HM-C is in the first step, where the initial planet masses and radii are drawn (HMC draws clustered initial masses as in §2.2.2, while HM-U does not). The planets are also assigned envelope masses in this step. The planets are then subject to photoevaporation and some lose their gaseous envelopes, resulting in the final masses and radii (§2.2.3). Finally, the critical AMD of the system is computed and distributed among the individual planets to draw their orbital eccentricities and mutual inclinations, as in the H20 model. -- astro-ph.EP

Exoplanets, -moons, -comets, Status Report, Stellar Cartography

Architectures of Exoplanetary Systems. IV: A Multi-planet Model for Reproducing the Radius Valley and Intra-system Size Similarity of Planets around Kepler’s FGK Dwarfs

by Keith CowingJanuary 30, 2026January 30, 2026

The Kepler-observed distribution of planet sizes have revealed two distinct patterns: (1) a radius valley separating super-Earths and sub-Neptunes and (2) a preference for intra-system size similarity.

The Kepler exoplanet candidate population around FGK stars used in the analysis of S. Bryson et al. (2021), shown in period and radius, both colored and sized by catalog reliability with exoplanet radius error bars. The background color map and contours indicate detection completeness. The rectangles show example η⊕ definitions from different authors. Adapted from S. Bryson et al. (2020a). -- astro-ph.EP

Astrogeology, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Status Report, Stellar Cartography, Water/Hycean Worlds & Oceanography

Why Estimating η⊕ Is Difficult: A Kepler-Centric Perspective

by Keith CowingDecember 29, 2025December 29, 2025

η⊕, the occurrence rate of rocky habitable zone exoplanets orbiting Sun-like stars, is of great interest to both the astronomical community and the general public. The Kepler space telescope has […]