Reliable Detections of Atmospheres on Rocky Exoplanets with Photometric JWST Phase Curves
The Astrophysical Journal Letters American Astronomical Society 978:2 (2025) L40
Abstract:
The prevalence of atmospheres on rocky planets is one of the major questions in exoplanet astronomy, but there are currently no published unambiguous detections of atmospheres on any rocky exoplanets. The MIRI instrument on JWST can measure thermal emission from tidally locked rocky exoplanets orbiting small, cool stars. This emission is a function of their surface and atmospheric properties, potentially allowing detections of atmospheres. One way to find atmospheres is to search for lower dayside emission than would be expected for a blackbody planet. Another technique is to measure phase curves of thermal emission to search for nightside emission due to atmospheric heat redistribution. Here, we compare strategies for detecting atmospheres on rocky exoplanets. We simulate secondary eclipse and phase curve observations in the MIRI F1500W and F1280W filters for a range of surfaces (providing our open-access albedo data) and atmospheres on 30 exoplanets selected for their F1500W signal-to-noise ratio. We show that secondary eclipse observations are more degenerate between surfaces and atmospheres than suggested in previous work, and that thick atmospheres can support emission consistent with a blackbody planet in these filters. These results make it difficult to unambiguously detect or rule out atmospheres using their photometric dayside emission alone. We suggest that an F1500W phase curve could instead be observed for a similar sample of planets. While phase curves are time-consuming and their instrumental systematics can be challenging, we suggest that they allow the only unambiguous detections of atmospheres by nightside thermal emission.A Comprehensive Analysis of Spitzer 4.5 μm Phase Curves of Hot Jupiters
The Astronomical Journal American Astronomical Society 169:1 (2025) 32
CRIRES+ and ESPRESSO Reveal an Atmosphere Enriched in Volatiles Relative to Refractories on the Ultrahot Jupiter WASP-121b
The Astronomical Journal American Astronomical Society 169:1 (2025) 10
Barotropic Instability
Chapter in Reference Module in Earth Systems and Environmental Sciences, Elsevier (2025)
Abstract:
Barotropic instability represents a class of instabilities, usually of parallel shear flows, for which gravity and buoyancy play a negligible role, at least in their energetics. It is not restricted to purely barotropic fluids (for which ρ = ρ(p), where ρ is density and p is pressure) but can also apply to flows which are stratified and exhibit vertical shear, often leading to instabilities with mixed barotropic and baroclinic characteristics. The primary attribute of barotropic instability is usually taken to be the dominance of energy exchanges in which the kinetic energy of a perturbation grows principally at the expense of the kinetic energy of the basic state. Here we present an introduction to the basic mechanisms involved and the factors that determine the necessary and/or sufficient conditions for instability. Several examples are presented and the occurrence and subsequent nonlinear evolution of the instability is illustrated with reference to both laboratory experiments and observations in the atmospheres and oceans of the Earth and other planets in the Solar System.
Limits on the atmospheric metallicity and aerosols of the sub-Neptune GJ 3090 b from high-resolution CRIRES+ spectroscopy
Monthly Notices of the Royal Astronomical Society, Volume 538, Issue 4, pp.3263-3283
Abstract:
The sub-Neptune planets have no solar system analogues, and their low bulk densities suggest thick atmospheres containing degenerate quantities of volatiles and H/He, surrounding cores of unknown sizes. Measurements of their atmospheric composition can help break these degeneracies, but many previous studies at low spectral resolution have largely been hindered by clouds or hazes, returning muted spectra. Here, we present the first comprehensive study of a short-period sub-Neptune using ground-based, high-resolution spectroscopy, which is sensitive to the cores of spectral lines that can extend above potential high altitude aerosol layers. We observe four CRIRES+ K-band transits of the warm sub-Neptune GJ 3090 b (T eq = 693 ± 18 K) which orbits an M2V host star. Despite the high quality data and sensitivity to CH4, H2O, NH3, and H2S, we detect no molecular species. Injection-recovery tests are consistent with two degenerate scenarios. First, GJ 3090 b may host a highly metal-enriched atmosphere with > 150 Z ⊙ and mean molecular weight > 7.1 g mol −1, representing a volatile dominated envelope with a H/He mass fraction xH/He<33 per cent, and an unconstrained aerosol layer. Second, the data are consistent with a high altitude cloud or haze layer at pressures < 3.3 ×10−5 bar, for any metallicity. GJ 3090 b joins the growing evidence to suggest that high metallicity atmospheres and high altitude aerosol layers are common within the warm (500 < Teq < 800 K) sub-Neptune population. We discuss the observational challenges posed by the M-dwarf host star, and suggest observing strategies for transmission spectroscopy of challenging targets around M-dwarfs for existing and ELT instrumentation.