Sub-Neptunes Archives

TESS observations of TOI-904. Panel (a): Raw observations of each TESS sector, with 2-minute data shown in light grey and 10-minute binned data shown in dark grey. We show the Tukey biweight trend calculated with the wotan (Hippke et al. 2019) library of the variability is shown in dark blue. Each planet transit is denoted by an arrow at the bottom of the graph, with blue denoting transits of TOI-904 b and gold denoting transits TOI-904 c. Panel (b): TESS data detrended by the same fit, with each transit high-lighted in the same color as the arrows in the previous figure. Panel (c): The phase folded light curves of transits of TOI-904 b with the transit fit including a shaded region denoting 1σ uncertainty. Panel (d): The phase-folded light curves of TOI-904 c with the transit fit including a shaded region denoting 1σ uncertainty. -- astro-ph.EP

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

Separated Twins Or Just Siblings? A Multi-planet System Around An M Dwarf Including A Cool sub-Neptune

by Keith CowingOctober 24, 2023October 24, 2023

We report the discovery of two TESS sub-Neptunes orbiting the early M dwarf TOI-904 (TIC 261257684). Both exoplanets, TOI-904 b and c, were initially observed in TESS sector 12 with […]

Similar to Figure 6, but here Tint is held constant at a value of 40 K, and cloud-top pressure (large grid cells) and water abundance (smaller embedded grid cells — see zoom-in panel at lower left) are varied as the two parameters of interest. In the absence of impact of clouds, the large grid cells should look identical to Figure 6, mirrored over the upper-left to lower-right diagonal (e.g. see the upper left-hand large grid cells). The presence of low-pressure (high-altitude) clouds alter the degree of degeneracy between spectra, as detailed in the text. -- astro-ph.EP

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Status Report, Water/Hycean Worlds & Oceanography

Where Are The Water Worlds?: Self-Consistent Models of Water-Rich Exoplanet Atmospheres

by Keith CowingJuly 13, 2023July 13, 2023

It remains to be ascertained whether sub-Neptune exoplanets primarily possess hydrogen-rich atmospheres or whether a population of H2O-rich “water worlds” lurks in their midst.

Result of planet evolution simulations in the orbital period–transit radius plane at 5 Gyr (left panel: energy-/recombination-limited model; right panel: hydrodynamic model). Each dot represents a planet which is coloured based on the fraction of its initial H/He envelope mass that was evaporated. Grey symbols indicate complete loss of the envelope, corresponding to sub-Neptunes that have evolved into super-Earths. The magenta lines show the fit to determine the slope α of the valley as represented by the largest super-Earth at a given period (i.e. the bottom of the valley). We note the shallower slope in the hydrodynamic model. The squares show two individual cases (one far planet in lilac, one close in black). Both start with identical initial conditions in the two models and are discussed in Sect. 4.2. They end up on different sides of the valley in the two models in a way to make the slope shallower in the hydrodynamic model. -- astro-ph.EP

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

Planetary Evolution With Atmospheric Photoevaporation II: Fitting The Slope Of The Radius Valley By Combining Boil-off And XUV-driven Escape

by Keith CowingJuly 7, 2023July 7, 2023

The Kepler satellite has revealed a gap between sub-Neptunes and super-Earths that atmospheric escape models had predicted as an evaporation valley.

TESS target pixel file images of TOI-2084 observed in Sector 16 (left panel) and TOI-4184 observed in Sector 1 (right panel), made by tpfplotter (Aller et al. 2020). Red dots show the location of Gaia DR3 sources, and the red shaded region shows the photometric apertures used to extract the photometric measurements. -- astro-ph.EP

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

TOI-2084 b and TOI-4184 b: Two New Sub-Neptunes Around M Dwarf Stars

by Keith CowingJune 28, 2023June 28, 2023

We present the discovery and validation of two TESS exoplanets orbiting nearby M dwarfs: TOI-2084b, and TOI-4184b. We characterized the host stars by combining spectra from Shane/Kast and Magellan/FIRE, SED […]

Model transmission spectrum of our canonical Hycean world K2-18 b. The model spectrum with all the molecules included is shown in grey. The spectra with the individual contributions of the different molecular species are shown as denoted in the legend. The synthetic JWST observations corresponding to the full model are shown as the gold-centered black points with error bars binned to a resolution of R= 40. The observations include one transit with NIRISS SOSS, three transits with NIRSpec G395H and two transits with MIRI LRS, as discussed in section 4. -- astro-ph.EP

Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Status Report, Water/Hycean Worlds & Oceanography

Chemical Conditions On Hycean Worlds

by Keith CowingJune 26, 2023June 26, 2023

Traditionally, the search for life on exoplanets has been predominantly focused on rocky exoplanets. Hycean worlds are a class of habitable sub-Neptunes with planet-wide oceans and H2-rich atmospheres. Their broad […]

Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Neptune, Status Report

Atmospheric Chemistry of Secondary and Hybrid Atmospheres of Super Earths and Sub-Neptunes

by Keith CowingJanuary 25, 2023June 19, 2023

The atmospheres of small exoplanets likely derive from a combination of geochemical outgassing and primordial gases left over from formation.

Astronomy & Telescopes, Atmospheres, Climate, Weather, Exoplanets, -moons, -comets, Neptune

Inferring Shallow Surfaces On sub-Neptune Exoplanets With JWST

by Keith CowingNovember 14, 2021June 19, 2023

Planets smaller than Neptune and larger than Earth make up the majority of the discovered exoplanets. Those with H2-rich atmospheres are prime targets for atmospheric characterization. The transition between the […]

Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Neptune

Possibilities for an Aerial Biosphere in Temperate Sub Neptune-Sized Exoplanet Atmospheres

by Keith CowingJune 16, 2021June 19, 2023

The search for signs of life through the detection of exoplanet atmosphere biosignature gases is gaining momentum. Yet, only a handful of rocky exoplanet atmospheres are suitable for observation with […]

Sub-Neptunes

Separated Twins Or Just Siblings? A Multi-planet System Around An M Dwarf Including A Cool sub-Neptune

Where Are The Water Worlds?: Self-Consistent Models of Water-Rich Exoplanet Atmospheres

Planetary Evolution With Atmospheric Photoevaporation II: Fitting The Slope Of The Radius Valley By Combining Boil-off And XUV-driven Escape

TOI-2084 b and TOI-4184 b: Two New Sub-Neptunes Around M Dwarf Stars

Chemical Conditions On Hycean Worlds

Atmospheric Chemistry of Secondary and Hybrid Atmospheres of Super Earths and Sub-Neptunes

Inferring Shallow Surfaces On sub-Neptune Exoplanets With JWST

Possibilities for an Aerial Biosphere in Temperate Sub Neptune-Sized Exoplanet Atmospheres

NASA Spaceline Current Awareness List #1,206 2 July 2026 (Space Life Science Research Results)

Older Than The Sun: Astronomers Find New Clues To The Origin Of Interstellar Comet 3I/ATLAS

Carl Sagan Month: Call For Participation

The Habitable Worlds Observatory Technology Development Plan

Searching For The Elusive CH2+ With The James Webb Space Telescope. Another Carbocation To Constrain Astrochemical Networks