[astro-ph.EP] Thousands of sub-Neptunes have been discovered mainly through space-based surveys such as Kepler and TESS. Their bulk compositions and internal structures are thought to reflect their formation and evolutionary […]
sub-Neptune
![Clouds may form via heterogeneous nucleation on top of ‘seed’ photochemical haze particles. Whether or not this pathway dominates over homogeneous nucleation—the process through which ‘pure’ clouds spontaneously form—depends on the microphysical contact angle between the relevant cloud and haze species. Smaller contact angles correspond to stronger cloud-haze interactions due to the increased affinity between the clouds and hazes. While this contact angle is unknown in the absence of lab data, heterogeneous nucleation is the primary cloud-formation pathway across the Solar System. -- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/08/Wet-Removal.png?resize=1200%2C715&ssl=1)
Posted inAtmospheres, Climate, Weather
Wet Removal and Cloud Enhancement: The Microphysics of Cloud-Haze Interactions on Sub-Neptunes
[astro-ph.EP] Aerosols are a near-ubiquitous feature of sub-Neptune atmospheres, yet their microphysical nature remains poorly understood. Both condensate clouds and photochemical hazes have been proposed to explain observations, but have […]
![Mass-radius diagram of known exoplanets together with model curves taken from A. Aguichine et al. (2021) and L. Zeng et al. (2019). Exoplanet data shown with colored dots were taken from the NASA Exoplanet Archive (J. L. Christiansen et al. 2025) on April 2, 2026. The transiting exoplanets in the HD 191939 system are highlighted with larger markers, error bars and a red outline.-- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/08/The-SPACE.png?resize=1200%2C714&ssl=1)
Posted inExoplanets, -moons, -comets
The SPACE Program II: No Discernible Spectral Features In The Transmission Spectrum Of The sub-Neptune HD 191939 b Observed With HST/WFC3
[astro-ph.EP] The atmospheres of sub-Neptunes provide a window into their internal structure and history, shedding light on the origin of this common, but enigmatic, class of exoplanets.
Posted inExoplanets, -moons, -comets
Exploration Of Exoplanet Atmospheres With The James Webb Space Telescope
[astro-ph.EP] The James Webb Space Telescope (JWST) is providing transformative characterization capabilities for the study of both transiting and directly imaged extrasolar planets. Observations deep into the infrared in the […]
Posted inExoplanets, -moons, -comets
Constraining The Lives And Times Of Exoplanets Through Evolutionary Bayesian Retrievals
[astro-ph.EP] Static retrieval frameworks are leading tools for interpreting exoplanet observations, yet time-independent modelling leaves them prone to degeneracy and unable to resolve exoplanets’ histories.
Posted inStellar Cartography
TESS Photometry and Radial Velocity Analysis of the sub-Neptune Exoplanet π Mensae c and the Wider π Mensae Planetary System
[astro-ph.EP] Exoplanet characterization relies on precise measurements of planetary orbital and physical parameters. This is particularly important for planetary dynamics and atmospheric evolution, as orbital parameters help constrain system evolution, […]
Posted inExoplanets, -moons, -comets
Distant Exoplanets May Be Hiding Water Beyond Webb Telescope’s Reach, Study Finds
[University of Chicago] The planets that appear most common in the universe could have a lot of water—but it could be hiding where telescopes can’t detect it, according to a […]
![Schematic showing the thermal and atmospheric escape evolution of two interpretations of sub-Neptune interiors. In a standard planetary model, a silicate interior is distinct from a hydrogen-rich envelope. As the planet contracts, hydrogen is removed from the upper atmosphere via stellar heating, and the interior-envelope boundary does not significantly contract with time. The temperature at this interface can reach of order ∼ 10, 000 K at early ages. In the miscible model, the interior-envelope boundary is defined by a binodal surface, which delineates regions in which hydrogen and silicate are miscible or immiscible. The temperature at the binodal surface does not change significantly with time. The radial position of the binodal surface contracts with time, exsolving hydrogen into the base of the envelope, while hydrogen is also removed from the top of the upper atmosphere.-- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/07/Testing-the.png?resize=1200%2C716&ssl=1)
Posted inExoplanets, -moons, -comets
Testing The Prevalence Of Hydrogen-silicate Miscibility In Young Sub-Neptunes
[astro-ph.EP] Hydrogen-silicate miscibility can significantly alter the interior structure and thermal evolution of sub-Neptunes. We consider the interplay between this miscibility and stellar-driven atmospheric escape.
Posted inExoplanets, -moons, -comets
Nautilus Space Observatory: Unveiling the Diversity and Origin of Sub-Neptunes
[astro-ph.IM] Sub-Neptunes are the most common class of planets in the Galaxy, yet they have no Solar System analog and remain poorly understood as a population. JWST observations have revealed […]
Posted inExoplanets, -moons, -comets
The Mid-Infrared Transmission Spectrum of the Temperate Sub-Neptune TOI-270 d
[astro-ph.EP] Observations of temperate sub-Neptunes with JWST have ushered in a new era for atmospheric characterization of small exoplanets.