Hycean exoplanet Archives - Astrobiology

Simulated thermal emission spectra from 0.6 to 15 µm of a CARMA model, EddySed models with various Scloud values and different fractions of the cloud mass mixing ratio, and a cloud-free model for a Y dwarf with Teff = 175 K, log(g) = 4.5 and fsed = 6. The inset highlights the region of interest between 3.5 - 6 µm. -- astro-ph.EP

Atmospheres, Climate, Weather, Brown Dwarfs, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Imaging & Spectroscopy, Status Report, Water/Hycean Worlds & Oceanography

Microphysical Prescriptions for Parameterized Water Cloud Formation on Ultra-cool Substellar Objects

by Keith CowingAugust 20, 2024

Water must condense into ice clouds in the coldest brown dwarfs and exoplanets. When they form, these icy clouds change the emergent spectra, temperature structure, and albedo of the substellar […]

Model transmission spectra used for cross-correlation. Top: Transmission spectra with contributions from H2O (blue), CH4 (brown) and NH3 (green), with the spectral baseline set by H2-H2 and H2-He collision-induced absorption. Bottom: Cloud-free and cloudy transmission spectra for the CH4 model with a grey-opacity cloud deck placed at various cloud top pressures. The cloud-free spectrum shown in brown is the same in both figures. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Exoplanets, -moons, -comets, Status Report, Water/Hycean Worlds & Oceanography

High-resolution Spectroscopic Reconnaissance Of A Temperate Sub-Neptune

by Keith CowingMarch 29, 2024

The study of temperate sub-Neptunes is the new frontier in exoplanetary science. A major development in the past year has been the first detection of carbon-bearing molecules in the atmosphere […]

Transmission spectrum of TOI-270 d observed with JWST/NIRSpec G395H and HST/WFC3. The NIRSpec G395H spectrum between 2.7 - 5.2 µm, from this work, is shown in dark red, binned to R ≈ 55 for visual clarity. The WFC3 spectrum is shown in orange and spans 1.1 - 1.6 µm, reported by Mikal-Evans et al. (2023). The retrieval is performed using the native resolution NIRSpec G395H spectrum (R ∼ 2700) and the WFC3 spectrum. The NIRSpec spectrum is vertically offset by −84 ppm, corresponding to the median retrieved offset in the canonical one-offset case. The blue curve shows the median retrieved model spectrum, while the medium- and lighter-blue contours denote the 1σ and 2σ intervals, respectively. Yellow points correspond to the median spectrum binned to match the observations. The prominent molecules responsible for the features in different spectral regions are labelled. -- astro-ph.EP

Astrochemistry, Astrogeology, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report, Water/Hycean Worlds & Oceanography

Possible Hycean Conditions In The sub-Neptune TOI-270 d

by Keith CowingMarch 7, 2024March 7, 2024

The JWST has ushered in a new era in atmospheric characterisations of temperate low-mass exoplanets with recent detections of carbon-bearing molecules in the candidate Hycean world K2-18 b.

Habitable Zones, Status Report

JWST Observations Of K2-18b Can Be Explained By A Gas-rich Mini-Neptune With No Habitable Surface

by Keith CowingJanuary 24, 2024January 23, 2024

JWST recently measured the transmission spectrum of K2-18b, a habitable-zone sub-Neptune exoplanet, detecting CH4 and CO2 in its atmosphere.

This artist’s concept shows what exoplanet K2-18 b could look like based on science data. K2-18 b, an exoplanet 8.6 times as massive as Earth, orbits the cool dwarf star K2-18 in the habitable zone and lies 120 light-years from Earth. A new investigation with NASA’s James Webb Space Telescope into K2-18 b has revealed the presence of carbon-bearing molecules including methane and carbon dioxide. The abundance of methane and carbon dioxide, and shortage of ammonia, support the hypothesis that there may be a water ocean underneath a hydrogen-rich atmosphere in K2-18 b. Credits: Illustration: NASA, CSA, ESA, J. Olmsted (STScI), Science: N. Madhusudhan (Cambridge University)

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Imaging & Spectroscopy, Press Release

Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18 b

by Keith CowingSeptember 11, 2023September 11, 2023

A new investigation with NASA’s James Webb Space Telescope into K2-18 b, an exoplanet 8.6 times as massive as Earth, has revealed the presence of carbon-bearing molecules including methane and […]