Born to Be Habitable: How the First Moments of Planet Formation Shape Worlds Like Ours
The paper argues that a planet’s ability to host life is shaped very early, during its formation in the protoplanetary disk. Farcy and collaborators highlight how bulk composition, volatile elements, core structure, and internal heat all arise from these initial conditions and later control atmospheres, magnetic fields, and surface environments. They conclude that comparative planetology, studying planets alongside their host stars, is essential for understanding how habitable worlds emerge.
A Fossil Star Without Planets? A High-Precision Look at BD+44°493
BD+44°493 is an ancient, extremely metal-poor star whose chemistry preserves the imprint of a single early-Universe supernova. Using new high-precision NEID spectra, the authors refined its elemental abundances, age, and Galactic orbit, confirming it as a second-generation star about 12–13 billion years old. Ultra-precise radial velocities show no evidence of planets and rule out companions more massive than ~2 Jupiter masses on short orbits.
Milky Way Worlds: A High-Resolution Look at Our Galaxy’s Exoplanets
The paper combines detailed Milky Way simulations with planet-formation models to predict exoplanet populations across the Galaxy. In the simulated solar neighbourhood, most planets are Earth-like or super-Earth/Neptunes, with about a quarter in the habitable zone. A forward model of the Kepler field reproduces many observed trends but overpredicts planets around hotter stars. Across different Galactic regions and simulated galaxies, planet-type proportions remain broadly consistent.
Where Planets Become Brown Dwarfs: Tracing a Hidden Boundary in the Metal Content of Stars
Giacalone et al. analyze companions between 1–50 au and find that host-star metallicities split into two groups at a transition mass of about 27 MJup. Lower-mass companions orbit metal-rich stars, consistent with bottom-up planet formation, while higher-mass companions orbit stars with near-solar metallicity, indicating star-like formation. Orbital eccentricities also differ, supporting two distinct formation pathways.
Are We There Yet? Understanding How Often Earth-like Worlds Exist Around Other Stars
Rachel Fernandes and colleagues review the difficulty of determining η⊕, the fraction of Sun-like stars hosting Earth-like planets in the habitable zone. Using Kepler data, they find estimates vary widely due to differing definitions, limited detections, and hidden factors like binary stars, planet multiplicity, and stellar chemistry. They conclude that future missions and improved data will be essential to refine η⊕ and guide the search for life.
When Impacts Bring Back the Air: How Collisions Could Revive Atmospheres on M-Dwarf Worlds
Prune C. August and colleagues show that rocky planets orbiting M-dwarf stars may repeatedly lose and regain their atmospheres. When gases like CO₂ freeze on the nightside, meteorite impacts can re-vaporize them, temporarily restoring an atmosphere. Their models predict that such planets could spend up to 80% of their lifetimes with these transient atmospheres, reshaping how astronomers interpret atmospheric “non-detections.”
Tracing Planet Formation Through Stellar Fingerprints: A Spectroscopic Look at C/O Ratios in Directly Imaged Exoplanet Hosts
Baburaj et al. conducted a high-resolution spectroscopic survey of five stars hosting directly imaged exoplanets to measure their elemental abundances. They found solar-like C/O ratios for HR 2562, AB Pic, and YSES 1, but significantly sub-solar ratios for PZ Tel and β Pictoris. These differences suggest diverse formation environments and highlight how stellar chemistry can trace planet formation processes.
Tracing the Chemistry of Exoplanet Hosts: What K2 Stars Reveal About Planets and Their Parent Stars
Loaiza-Tacuri et al. analyzed 301 K2 exoplanet-hosting stars using high-resolution spectra to measure stellar temperatures, metallicities, magnesium abundances, and activity levels. They confirmed the planetary radius gap near 1.9 R⊕, found that larger planets orbit more metal-rich stars, and showed stellar activity decreases with planet size. Most hosts belong to the Galactic thin disk, linking stellar chemistry to planetary formation.
A Planet of Fire and Gas: How Magma Oceans May Explain TOI-270 d’s Mysterious Atmosphere
Matthew C. Nixon and collaborators show that magma-ocean interactions between TOI-270 d’s molten interior and gaseous atmosphere can naturally explain JWST’s detection of H₂O, CH₄, and CO₂ without invoking icy material. Their integrated models link interior chemistry to observable spectra, reproducing the planet’s high metallicity and low C/O ratio. This work suggests that sub-Neptunes’ atmospheres may be strongly shaped by deep, ongoing magma processes.
Peering Into TRAPPIST-1e: JWST’s First Glimpses of a Habitable-Zone Rocky World
Espinoza and collaborators used JWST to observe four transits of TRAPPIST-1 e, a rocky planet in the habitable zone. They found that stellar activity strongly contaminates the data but developed new statistical methods to handle it. Their results rule out a thick hydrogen-rich atmosphere, suggesting TRAPPIST-1 e, if it has an atmosphere, likely hosts heavier gases such as carbon dioxide.
TRAPPIST-1 d: Searching for Signs of Air on a Nearby Earth-Sized World
Astronomers used JWST to study TRAPPIST-1 d, an Earth-sized planet near the habitable zone of its star. The data revealed a flat transmission spectrum, ruling out thick atmospheres of hydrogen, methane, water vapor, or carbon dioxide. This suggests TRAPPIST-1 d is either airless, has only a very thin atmosphere, or is shrouded by high-altitude clouds, offering key insights into how rocky planets around small stars evolve.
Tracing the Heavy Elements: How Neutron-Capture Chemistry Connects Stars and Planets
Sharma et al. studied 160 planet-hosting stars, measuring nine neutron-capture elements to explore links between stellar chemistry and planet formation. Most abundances match normal Galactic evolution, but zirconium, lanthanum, and cerium are often enhanced. In giant stars, several elements correlate with higher planet masses. Younger, metal-rich systems tend to be richer in refractory elements, hinting at possible chemical fingerprints of planet formation.
Hunting for Air: Testing the Cosmic Shoreline Around M Stars with JWST
The paper by Jegug Ih and collaborators uses simulations and statistical modeling to determine whether rocky planets around M stars have atmospheres. By framing target selection as an optimization problem, they test different observation strategies with JWST. Results show that a “wide and shallow” survey can efficiently limit atmospheric occurrence rates and, if a Cosmic Shoreline exists, detect it within ~500 hours.
A Hot Super-Neptune on the Edge: Unveiling TOI-5795 b
TOI-5795 b is a hot super-Neptune orbiting a metal-poor, Sun-like star every 6.14 days. It likely lost part of its atmosphere to stellar radiation and may have formed through complex or violent processes, not well explained by standard models. Its low density and location at the edge of the Neptune desert make it ideal for future atmospheric studies.
Mind the Gap: How Missing One Planet Can Skew Our View of Alien Solar Systems
Thomas et al. investigate how missing a planet affects our view of exoplanet systems. They find that removing a planet, especially one from the middle, disrupts the regular spacing (gap complexity) but doesn't affect planet mass similarity or system flatness. This supports the idea that uniform planetary spacing is an intrinsic feature, not just a detection bias.
A Cool Ocean World Beyond Earth? JWST Reveals K2-18 b’s Watery Interior
Renyu Hu et al. used JWST to study the atmosphere of K2-18 b, a temperate sub-Neptune. They detected methane and carbon dioxide but no water vapor, suggesting a water-rich interior beneath a thin hydrogen atmosphere. The findings hint at a possible liquid-water ocean, though alternative models remain plausible.
Do Planets Steal a Star's Lithium? A New Look at 450 Stars
This study analyzed 450 stars to test whether having planets affects a star's lithium levels. Using high-resolution data and careful comparisons, the authors found no significant difference in lithium abundance between stars with and without planets. Factors like stellar mass and age explain lithium variation better than planet presence.
Grand Theft Moons: How Giant Planets Might Steal Their Way to Habitability
This study explores how moons around giant exoplanets might form and become habitable, especially due to tidal heating. Simulations show that planets around 2 AU from their stars produce the most promising moons. Some moons may escape the planet’s grip due to stellar gravity, but about 32% could still be habitable, expanding the search for life beyond Earth-like planets.
From Pebbles to Planets: Exploring the Rich Diversity of Small Worlds Beyond Our Solar System
This review explores the diverse worlds of low-mass exoplanets, focusing on how they form, what they're made of, and how we study them using tools like JWST. It highlights the importance of planet size, disk structure, and atmospheric loss, and even examines clues from planets orbiting dead stars. These findings offer key insights into how Earth-like planets may form and evolve.
Reading Planetary Surfaces in the Skies: How Exoplanet Atmospheres Reveal Their Rocky Roots
Herbort and Sereinig model how rocky exoplanet surfaces influence their atmospheres, showing that specific gases and clouds in an atmosphere can hint at underlying rock types. Using chemical equilibrium models and simulated spectra, they find links between atmospheric composition and crustal minerals. This research helps interpret telescope data to infer exoplanet surface composition.