![Radial velocity timeseries of K2-3 used in the analysis. Here the second dimension for the multi-dimensional quasi-periodic gaussian process kernes used the D2V activity indicator to disentangle the stellar activity from the Keplerian signals. The Keplerian models for all three planets are assumed to be circular orbits for this figure (Model 1 in Table C.3). The various instruments used in the analysis are colour coded. -- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/09/Uncovering.png?resize=1200%2C719&ssl=1)
[astro-ph.EP] The K2-3 system is one of the most unique planetary systems as it features three transiting sub-Neptunes in decreasing order of radii, spanning the radius valley.
astro-ph.EP
![Post-processed NIRCam images for the two epochs, with 1- and 2-σ contours of the expected position, computed with the posteriors of the Octofitter results: in white without including the images in the fit, and in green including the images, but without making a connection between flux and atmospheric model. The postprocessing method is described in Sec. 2.3. When including the images, some walkers tend towards the feature whose location coincides with the expected position of planet b. -- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/09/An-Updated.png?resize=1200%2C719&ssl=1)
Posted inEpsilon Eridani
An Updated Model For Epsilon Eridani b and Prospects for Imaging With The Roman Coronagraph
[astro-ph.EP] Epsilon Eridani b, the nearest known Jupiter analog, has its orbit and mass constrained from radial velocity (RV) and absolute astrometry, and its atmosphere from JWST/NIRCam imaging upper limits […]
![Log–log relation between age and rotation period for M dwarfs. Black squares show the Engle & Guinan (2023) sample. Filled circles are cluster members from Curtis et al. (2020) and Godoy-Rivera et al. (2021), colour-coded by spectral type (M2–M6). The solid blue curve is the median fit. Dark- and light-grey bands denote the 68% and 95% posterior predictive regions, including intrinsic astrophysical scatter. Triangles with error bars indicate the target stars analysed in this work. -- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/09/Stellar.png?resize=1200%2C720&ssl=1)
Posted inStellar Cartography
Stellar Ages of M Dwarf Hosts of Temperate Sub-Neptunes
[astro-ph.EP] Measuring M dwarf ages is a central challenge in stellar astrophysics. These stars evolve so slowly that isochrone fitting gives little constraint, requiring alternative methods based on rotation, activity, […]
![Overview of the gas-phase oxygen and carbon chemistry in hydrogen-dominated planetary atmospheres.-- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/09/The-atomic.png?resize=1200%2C719&ssl=1)
Posted inExoplanets, -moons, -comets
The Atomic C/O Ratio Of Exoplanet KELT-9b
[astro-ph.EP] The carbon-to-oxygen (C/O) ratio of a giant planet’s atmosphere has long been theorised to hold compositional information that can be traced back to its formation history.
![Low-angle backscatter electron (LABE) imaging (Supplement 9) of sample OREX-220001-1 consisting of particles obtained from inside the SRC but exterior to the sample canister — including fragments of Bennu, SRC char, and metal. FG, fine-grained. -- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/09/OSIRIS-REx.png?resize=1200%2C800&ssl=1)
Posted inSample Return
OSIRIS-REx Returned a Pristine Sample of Asteroid Bennu: Takeaways from the Mission’s Contamination Control and Knowledge Program
[astro-ph.EP] NASA’s OSIRIS-REx mission had the objective of delivering a pristine sample from asteroid (101955) Bennu to Earth for scientific analysis–where “pristine” signifies the absence of foreign materials that could […]
Posted inExoplanets, -moons, -comets
JWST/MIRI Imaging Search for Kinematically Detected Protoplanetary Candidates
[astro-ph.EP] Kinematic perturbations observed with ALMA in CO line emission provide evidence for a population of embedded giant protoplanets shaping the structure of protoplanetary disks.
Posted inTRAPPIST-1
Radial Velocity Detection Of The TRAPPIST-1 Planetary System With SPIRou And NIRPS
[astro-ph.EP]. The TRAPPIST-1 system is well-known for its seven transiting Earth-sized exoplanets. It has been extensively studied and characterized, notably with transit timing variations (TTVs) to precisely measure the mass […]
![Simulated ablation heights of IDPs in exoplanet atmospheres. Our fiducial simulation is marked in red. Solid and dashed curves signify IDP compositions of MgSiO3 and Fe, respectively. The black dashed curve on the left most panel shows the approximation of the mass injection function Fv(p) for an arbitrary IDP mass flux for comparison with the ablation profiles. -- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/09/Interplanetary-Dust.png?resize=1200%2C721&ssl=1)
Posted inAstrogeology
Interplanetary Dust Ablation Seeds Silicate Clouds in Exoplanet Atmospheres
[astro-ph.EP] Interplanetary dust particles (IDPs) are present throughout the Solar System, with Earth experiencing a mass flux of roughly 100 tonnes of IDPs per day.
Posted inExoplanets, -moons, -comets
Two Extremely Irradiated Volatile-rich Sub-Neptunes With Companions In The TOI-426 And TOI-1839 Systems: Insights Into Arrival And Survival Near The Lower Edge Of The Neptunian Desert
[astro-ph.EP] Using TESS photometry and 147 HARPS radial velocities, we confirm two extremely irradiated, volatile-rich sub-Neptunes near the lower edge of the Neptunian desert: TOI-426 b and TOI-1839 b, orbiting […]
Posted inAtmospheres, Climate, Weather
Contrasting C/O Ratios in Uranus and Neptune From Disequilibrium Chemistry: A Clue To Distinct Evolutionary Pathways?
[astro-ph.EP] The formation of Uranus and Neptune remains poorly constrained largely due to uncertain deep elemental abundances. Carbon monoxide (CO), a disequilibrium species in the upper troposphere, provides an indirect […]