![Best-fitting spectrum and atmospheric properties of WD 1856 b. a. Spectral decomposition illustrating the model components required to explain WD 1856 b’s JWST transmission spectrum (FIREFLy reduction; orange circles with 1 σ error bars). The best-fitting model (black curve) contains absorption from multiple CH4 features (purple shading), H2 + He continuum absorption (dark grey shading), and tentative evidence of C2H6 near 3.4 µm (brown shading) and PH3 near 4.3 µm (orange shading). Aerosol continuum opacity (silver shading) blocks thermal emission from the deep atmosphere in windows between CH4 bands, obscuring the ‘negative spikes’ that would otherwise be observed near 0.7 µm, 2.9 µm, and longwards of 4.0 µm for a clear atmosphere. The best-fitting model without nightside thermal emission (blue dashed curve) cannot explain the significantly lower transit depths longwards of 3.5 µm. b. Retrieved atmospheric properties, planetary mass, and aerosol properties from WD 1856 b’s JWST transmission spectrum for the FIREFLy (orange histograms) and Juniper (green histograms) data reductions. The median (solid line) and 1 σ credible intervals for each parameter (dashed lines) are overlaid. c. Residuals between the data and best-fitting model. -- [astro-ph.EP]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/07/Aerosols.png?resize=1200%2C719&ssl=1)
[astro-ph.EP] Most stars, including our Sun, will one day evolve into red giants and, subsequently, white dwarfs. Several planet candidates have recently been identified orbiting white dwarfs, demonstrating that planets […]
Red Giant
Posted inAstrochemistry, Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Europa, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Status Report, Stellar Cartography
Life After Death: Europa In The Evolving Habitable Zone Of A Red Sun
Most stars end their main-sequence (MS) lives by evolving through the red-giant and asymptotic-giant branches before ending as a quiescent, stable white dwarf. Therefore, it is imperative to model the […]
![[C/N] versus log g for the APOGEE sample, with the same tracks and colouring as Figure 1. The samples in this paper with evolution tracks and the full DR17 samples for context. The lines are MIST stellar evolution tracks of 1 𝑀⊙ (dotted) and 1.6 𝑀⊙ (dashed) at solar metallicity. These tracks have markers denoting the onset, midpoint, and completion of the FDU as well as the beginning of re-contraction at the RGB bump. Due to the FDU beginning and ending slowly, the onset and completion are marked at the points where 10% and 90% of the total [C/N] change has occurred, respectively. Unlike the subgiants, not all giants from APOGEE are used because they are restricted to the APOKASC3 sample. -- astro-ph.SR](https://i0.wp.com/astrobiology.com/wp-content/uploads/2024/03/Nature-vs-Nurture.png?resize=1200%2C719&ssl=1)
Posted inAstrochemistry, Astronomy & Telescopes, Biochemistry & Organic Chemistry, Imaging & Spectroscopy, Status Report
Nature vs. Nurture: Distinguishing Effects from Stellar Processing and Chemical Evolution on Carbon and Nitrogen in Red Giant Stars
The surface [C/N] ratios of evolved giants are strongly affected by the first dredge-up (FDU) of nuclear-processed material from stellar cores. C and N also have distinct nucleosynthetic origins and […]
Posted inExoplanets, -moons, -comets, Habitable Zones, Status Report
Exoplanets Around Red Giants: Distribution And Habitability
As the search for exoplanets continues, more are being discovered orbiting Red Giant stars. We use current data from the NASA Exoplanet Archive to investigate planet distribution around Red Giant […]