TOI-270 d Archives - Page 2 of 2 - Astrobiology

A graphical summary of our most important findings with emphasis placed on the origin, fate, and context of “missing ammonia” in the atmosphere of TOI-270 d. Numbers indicate a sequence of processes that may result in a lack of detectable NH3. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Status Report

Deciphering Sub-Neptune Atmospheres: New Insights from Geochemical Models of TOI-270 d

by Keith CowingApril 17, 2025April 17, 2025

The nature of sub-Neptunes is one of the hottest topics in exoplanetary science. Temperate sub-Neptunes are of special interest because some could be habitable.

An SwRI-led study modeled the chemistry of TOI-270 d, a nearby exoplanet between Earth and Neptune in size, finding evidence that it is a giant rocky world (super-Earth) surrounded by a deep, hot atmosphere. - SwRI

Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Habitable Zones, Neptune, Press Release, Water/Hycean Worlds & Oceanography

Deciphering The Mysterious Atmosphere Of ‘Rosetta Stone’ Exoplanet TOI-270 d

by Keith CowingApril 15, 2025April 15, 2025

A Southwest Research Institute-led study modeled the chemistry of TOI-270 d, an exoplanet between Earth and Neptune in size, finding evidence that it could be a giant rocky planet shrouded […]

Artist’s impression shows the planet K2-18b, its host star and an accompanying planet in this system. ESA/Hubble, M. Kornmesser

Astrogeology, Atmospheres, Climate, Weather, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Habitable Zones, Icy Worlds, Origin & Evolution of Life, Press Release, Water/Hycean Worlds & Oceanography

Atmospheres Of New Planets Might Have Unexpected Mixtures Of Hydrogen And Water

by Keith CowingMarch 28, 2025March 28, 2025

Recent studies show that the most common type of planets in our galaxy, those between the sizes of Earth and Neptune, typically form with a hydrogen atmosphere, resulting in conditions […]

Masses and radii of well-constrained small planets (0.2 ≤ Mp ≤ 30 M⊕). This catalog is a subset of the NASA Exoplanet Archive showing planets with consistently measured masses (RV or TTV) and measured radii (transit). The points are color-coded by composition: On the left, as bulk water mass fraction (Aguichine et al. 2021) and on the right, as bulk H2/He mass fraction (Lopez & Fortney 2014). Composition lines are shown for an equilibrium temperature of 500 K; rocky and Earth-like predictions are from Zeng et al. (2016). Bold and labeled circle symbols show planets with published JWST transmission spectra, and bold and labeled star symbols show other published COMPASS targets. TOI-776 c (the subject of this paper) is shown in larger font/symbol. -- astro-ph.EP

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

JWST COMPASS: NIRSpec/G395H Transmission Observations of TOI-776 c, a 2 Rearth [Earth radius] M Dwarf Planet

by Keith CowingMarch 4, 2025March 4, 2025

The atmospheres of planets between the size of Earth and Neptune at short orbital periods have been under intense scrutiny.

Comparisons between the theoretical transmission spectra generated by EPACRIS (solid lines) and the JWST observations for (Top) H2:H2O=50:50 and [C+N+S]=100×solar metallicity scenario of K2-18 b assuming Ab = 0.3 corresponding to the left panel of Figure 4, and (Bottom) H2:H2O=75:25 and [C+N+S]=100×solar metallicity scenario of TOI-270 d assuming Ab = 0 corresponding to the right panel of Figure 4. The grey symbols with error bars indicate JWST observations of corresponding exoplanets taken from Madhusudhan et al. (2023) for K2-18 b (Top), and Benneke et al. (2024) for TOI-270 d (Bottom). Each color represents a spectrum generated by excluding specific species: green for no CH4, red for no CO2, light blue for no OCS, blue for no H2O, teal for no CO, light brown for no NH3, and black for all species included. -- astro-ph.EP

Astronomy & Telescopes, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Chemical Mapping of Temperate Sub-Neptune Atmospheres: Constraining The Deep-interior H2O/H2 Using The Atmospheric CO2/CH4

by Keith CowingJune 7, 2024June 7, 2024

Understanding the envelope composition of sub-Neptune-type exoplanets is challenging due to the inherent degeneracy in their interior composition scenarios. Particularly, the H2O/H2 ratio, or can be expressed as the O/H […]

Broadband and spectroscopic light-curve fits of the NIRISS/SOSS (left) and NIRSpec/G395H (right) transits of TOI-270 d. For both instruments, examples of 10 normalized and systematics-corrected light curves are shown (colored points) along with their best-fitting transit models (black lines) and labelled with the central wavelength of the spectroscopic channel. Broadband light-curve fits (white) are also shown at the top for Order 1 in the NIRISS/SOSS case, and for NRS1 in the NIRSpec/G395H case. For clarity, the spectroscopic light curves are plotted with a relative flux offset. For NIRSpec/G395H, light curves with wavelengths below 3.8 µm are from the NRS1 detector and the remaining from NRS2. For visual purposes, the light curves are also binned in time in groups of 10 (NIRISS/SOSS) and 20 (NIRSpec/G395H) data points, resulting in 3.6 minute bins. A full transit of planet b occurs at the start of the NIRSpec/G395H exposure, with both transits overlapping shortly as planet d starts transiting. All light curves are well-behaved, with no signs of spot-crossing events or Hα flares. -- astro-ph.EP

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

JWST Reveals CH4, CO2, and H2O in a Metal-rich Miscible Atmosphere on a Two-Earth-Radius Exoplanet

by Keith CowingMarch 7, 2024March 7, 2024

Even though sub-Neptunes likely represent the most common outcome of planet formation, their natures remain poorly understood.

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.