sub-Neptune Archives - Page 6 of 20 - Astrobiology

Results of full N -body simulations with the initial conditions eini = 0.8 and Nini = 80. (a) Impact velocities between SNs and embryos. (b) Atmospheric mass-loss fraction. (c) Total number of collisions. (d) Final remaining atmospheric mass fractions of SNs. (e) Final radius distribution of SNs at 50 Myr and the initial radius distribution. (f) Dependence of the final radius of SNs at 50 Myr and initial radius on orbital-period distribution. -- astro-ph.EP

Astrogeology, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Status Report

Long-Term Evolution of Close-in Sub-Neptunes and Outer Planetary Embryos: Atmospheric Mass Loss and Origin of Planets Inside and Outside the Radius Gap

by Keith CowingFebruary 13, 2026February 13, 2026

As a byproduct of sub-Neptune formation, planetary embryos with high eccentricity can remain in outer orbits, near 1 au from the star. In this work, we investigate the long-term evolution […]

Schematic of some of the key processes throughout planet formation that influence carbon supply and retention. (a) Key ice/grain sublimation fronts in the disk noted (CO2 between water–CO and that of Silicates at inner disk edge not shown). Planets forming in these locations will receive different compositions at birth (Öberg et al. 2011). Dust that grows beyond the “soot” line (Lodders 2004, Kress et al. 2010, Li et al. 2021) will be rich in refractory carbon content and at greater distances molecular ices. (blow-out:) The drift of carbon-rich pebbles from the outer disk is a key process in carbon supply. Drift itself is influenced by pressure bumps that can lead to a pile-up of pebbles that can be potential sites for planetesimal and planet formation (shown on left side of disk). (b) Solids accrete ice mantles, sublimate key components at sublimation fronts and can collide leading to both growth and fragmentation. (c) Rocky planets and cores of gas-rich planets grow and gain carbon through accretion of pebbles (top) and/or planetesimals (bottom). Impacts of larger planetesimals can also strip atmospheric gas and also supply material. (d) heavy element differentiation can take carbon to the core, and the resulting magma ocean/atmosphere equilibrium can influence atmospheric composition with lighter gases escaping depending on the planet mass. Figure credit to N. Fuller and Sayo Studio. -- astro-ph.EP

Astrochemistry, Astronomy & Telescopes, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Gas Giants, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Press Release

Carbon From Interstellar Clouds To Habitable Worlds

by Keith CowingFebruary 12, 2026February 12, 2026

Carbon is an essential element for a habitable world. Inner (r < 3 au) disk planetary carbon compositions are strongly influenced by supply and survival of carbonaceous solids. Here we […]

The observed sources and data collected during the K2-18b observing campaign. (Left) The dates of the observations and the frequencies in which signals were detected. (Right) The location of the 64 coherent beams (gray circles), the position of K2-18 (red star), and the FWHM PB for the MeerKAT telescope at L-band. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Intelligence & Language, SETI & Technosignatures, Status Report, Water/Hycean Worlds & Oceanography

A Narrowband Technosignature Search Toward The Hycean Candidate K2-18b Using The VLA And MeerKAT

by Keith CowingFebruary 11, 2026February 11, 2026

K2-18b, a sub-Neptune exoplanet located in the habitable zone of its host star, has emerged as an important target for atmospheric characterization and assessments of potential habitability.

Known potentially-rocky exoplanets within 20 pc. The vast majority of the closest planets are non-transiting and their atmospheres cannot be characterized with currently-available techniques. Data from the NASA Exoplanet Archive, accessed on 2026-02-06. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

A New Strategy For Using Spectroscopic Phase Curves to Characterize Non-Transiting Planets

by Keith CowingFebruary 10, 2026

We introduce a new time-series analysis strategy for combined-light exoplanet spectroscopic phase curves called the Variable Planetary Infrared Excess (VPIE) method. VPIE can be used to extract information about the […]

A planet with a magma ocean -- Grok via Astrobiology.com

Astrogeology, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Lava / magma ocean / Volcanic Worlds, Status Report

The Effects Of Non-ideal Mixing In Planetary Magma Oceans And Atmospheres

by Keith CowingFebruary 8, 2026February 8, 2026

Sub-Neptunes with hydrogen-rich envelopes are expected to sustain long-lived magma oceans that continuously exchange volatiles with their overlying atmospheres. Capturing these interactions is key to understanding the chemical evolution and […]

Astrogeology, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Icy Worlds, Imaging & Spectroscopy, Status Report, Water/Hycean Worlds & Oceanography

The Role of Intrinsic Temperature and Vertical Mixing in Characterizing Sub-Neptune Atmospheres

by Keith CowingJanuary 30, 2026January 30, 2026

Sub-Neptune planets are often modeled with a dense rocky or metal-rich interior beneath a thick hydrogen/helium (H/He) atmosphere; though their bulk densities could also be explained by a water-rich interior […]

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.

Mass mixing ratios and condensate/cloud of the O2/CO2 atmosphere - model 5. The 15 major gas phase species are shown in the left hand side column and the solid and liquid species in the right hand side column.

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

Hot And cloudy: High Temperature Clouds In Super-Earths And Sub-Neptunes

by Keith CowingJanuary 26, 2026January 26, 2026

JWST observations provide for the first time evidence for an atmosphere on a rocky exoplanet – 55 Cnc e. The atmosphere of 55 Cnc e is hot with Teq>2000K and […]

The PLL analysis of the fifth detected transit of TOI-5388 b at 1881.03 TBJD. Each square represents the flux of a pixel, with respect to time, and the color scale represent the average flux value. Yellow dots represent the expected transit time. The red contour represents the aperture mask for LC extraction. -- astro-ph.EP

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Characterization Of Two New Transiting Sub-Neptunes And A Terrestrial Planet Around M-dwarf Hosts

by Keith CowingJanuary 20, 2026January 20, 2026

We report the confirmation of three transiting exoplanets orbiting TOI-1243 (LSPM~J0902+7138), TOI-4529 (G~2–21), and TOI-5388 (Wolf~346) that were initially detected by TESS through ground-based photometry and radial velocity follow-up measurements […]

The posteriors were derived by applying the planetary evolution and mass loss framework of ref. 32 to our measured masses and radii for planets c (red), d (orange), b (green) and e (blue). Left, initial envelope mass fraction versus core mass. Right, initial Kelvin–Helmholtz cooling timescale versus core mass. Contours show the 1σ and 2σ credible regions. (Note that the jagged appearance of some contours is a numerical artefact of the discrete core mass grid used in our analysis; see Methods for more details). The vertical dotted line in the right panel at 10 Myr marks the approximate upper limit for standard high-entropy formation models. These models are strongly disfavoured for the inner planets c and d, whereas for the less-irradiated outer planets b and e, the method lacks the statistical power to distinguish between high- and low-entropy scenarios. -- Nature

Astrogeology, Astronomy & Telescopes, Exoplanets, -moons, -comets, Status Report

A Young Progenitor For The Most Common Planetary Systems In The Galaxy

by Keith CowingJanuary 16, 2026January 16, 2026

The Galaxy’s most common known planetary systems have several Earth-to-Neptune-size planets in compact orbits. At small orbital separations, larger planets are less common than their smaller counterparts by an order […]