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Star-like objects with effective temperatures of less than 2,700 kelvin are referred to as ultracool dwarfs. This heterogeneous group includes stars of extremely low mass as well as brown dwarfs (substellar objects not massive enough to…
We explore the heating and differentiation of rocky planets that grow by rapid pebble accretion. Our terrestrial planets grow outside of the ice line and initially accrete 28\% water ice by mass. The accretion of water stops after the…
Context: The principle definition of habitability for exoplanets is whether they can sustain liquid water on their surfaces, i.e. that they orbit within the habitable zone. However, the planet's magnetosphere should also be considered,…
Low-gravity waterworlds ($M\lesssim 0.1 M_{\oplus}$) are of interest for their potential habitability. The weakly bound atmospheres of such worlds have proportionally larger radiative surfaces and are more susceptible to escape. We conduct…
As of late 2025 there are about 70 exoplanets that meet the formal criterion of having equilibrium temperatures allowing the presence of liquid water and about 50 of them orbit M-stars, known for their strong chromospheric activity. Most of…
A variety of terrestrial planets with different physical parameters and exotic atmospheres might plausibly exist outside our Solar System, waiting to be detected by the next generation of space-exploration missions. Some of these planets…
Small rocky planets, as well as larger planets that suffered extensive volatile loss, tend to be drier and have thinner atmospheres as compared to Earth. Such planets probably outnumber worlds better endowed with volatiles, being the most…
The extra-solar planet HD209458b has been found to have an extended atmosphere of escaping atomic hydrogen (Vidal-Madjar et al. 2003), suggesting that ``hot Jupiters'' closer to their parent stars could evaporate. Here we estimate the…
The M-type star Gliese 581 is orbited by at least one terrestrial planet candidate in the habitable zone, i.e. GL 581 d. Orbital simulations have shown that additional planets inside the habitable zone of GL 581 would be dynamically stable.…
The Kepler data show that habitable small planets orbiting Red Dwarf stars (RDs) are abundant, and hence might be promising targets to look at for biomarkers and life. Planets orbiting within the Habitable Zone of RDs are close enough to be…
We explore the appearance of terrestrial planets in formation by studying the emergent spectra of hot molten protoplanets during their collisional formation. While such collisions are rare, the surfaces of these bodies may remain hot at…
Mass-radius relationships for water-rich rocky planets are usually calculated assuming most water is present in condensed (either liquid or solid) form. Planet density estimates are then compared to these mass-radius relationships, even…
Planets composed of large quantities of water that reside in the habitable zone are expected to have distinct geophysics and geochemistry of their surfaces and atmospheres. We explore these properties motivated by two key questions: whether…
Extreme instellation on lava planets causes the rocky surface to melt and vaporize. Because the rock vapour composition is intrinsically tied to the mantle, atmospheric characterization of lava planets can hold valuable insight into the…
Traditional definitions of the habitable zone assume that habitable planets contain a carbonate-silicate cycle that regulates CO2 between the atmosphere, surface, and the interior. Such theories have been used to cast doubt on the…
Our knowledge of planets' orbital dynamics, which was based on Solar System studies, has been challenged by the diversity of exoplanetary systems. Around cool and ultra cool dwarfs, the influence of tides on the orbital and spin evolution…
The recent discovery of an Earth-sized planet (TOI-700 d) in the habitable zone of an early-type M-dwarf by the Transiting Exoplanet Survey Satellite constitutes an important advance. In this Letter, we assess the feasibility of this planet…
A long-standing issue in astrobiology is whether planets orbiting the most abundant type of stars, M-dwarfs, can support liquid water and eventually life. A new study shows that subglacial melting may provide an answer, significantly…
Planets in the liquid-water habitable zone of low-mass stars experience large tidal forces, $10^3$ to $10^4$ times those on Earth, due to the small distance between the habitable zone and the host stars. Therefore, interior solid tides,…
A radiative-convective climate model is used to calculate stratospheric temperatures and water vapor concentrations for ozone-free atmospheres warmer than that of modern Earth. Cold, dry stratospheres are predicted at low surface…