Disentangling the hemispheres of Teegarden's Star b with LIFE

TL;DR

Teegarden's Star b is used as a test case to assess LIFE's ability to spatially disentangle hemispheres of a non-transiting, Earth-like planet. The study combines high-fidelity 3D climate modeling with synthetic instrument simulations to quantify hemisphere discrimination as a function of observation time and stellar type. Results show that for the tidally locked M-dwarf scenario, 3 days of broadband LIFE observations can achieve $1\sigma$ (baseline) or $3\sigma$ (optimistic) discrimination, while a Sun-like star scenario requires substantially longer integrations and yields weaker signals. The work implies LIFE can, with sufficient time, reconstruct coarse thermal maps and potentially detect water clouds and hydrology, contributing to assessments of habitability and atmospheric dynamics in temperate rocky exoplanets.

Abstract

Teegarden's Star is one of the most promising targets for the first observations of LIFE, as a non-transiting rocky planet with similar bulk properties to the Earth, and a relatively quiescent M-dwarf host star. We use LIFEsim, a software developed by the ETH LIFE team, along with thermal emission maps obtained from a suite of three-dimensional global climate model (GCM) simulations, to explore the sensitivity of LIFE to the observation geometry. We find that 3 days of observation in broadband would be enough to disentangle the hemispheres of the planet with a 1σ or 3σ confidence level with a baseline or optimistic scenario respectively. Doing the same for a fast-rotator in the habitable zone of a G-class star would be prohibitively challenging. Given enough observation time, the sensitivity of LIFE may allow some spatial resolution of Teegarden's Star b to be achieved, which may directly link to the presence of water clouds and therefore an active hydrology.

Figures (11)

• Figure 1: Outgoing longwave radiation of six potentially visible hemispheres of the planet.
• Figure 2: Cloud fraction averaged over all pressure levels.
• Figure 3: Broadband significance as a function of integration time for Teegarden's Star b, assuming an instellation of 1481 Wm$^{-2}$ and either a baseline or an optimistic scenario. The dayside hemisphere is taken as the reference.
• Figure 4: LIFEsim synthetic observation of Teegarden's Star b with a resolution of 50 and integration times of one week, one month, and two months assuming a baseline and an optimistic scenario. Rows 1 and 3 depict the thermal emission integrated over the six hemispheres of the planet. The shaded areas represent the 1$\sigma$ confidence level. Rows 2 and 4 show the statistical significance of the detected difference between the dayside and the other hemispheres.
• Figure 5: Integration time as a function of wavelength for Teegarden's Star b, assuming an instellation of 1481 Wm$^{-2}$ and either a baseline or an optimistic scenario. The dayside hemisphere is taken as the reference. White contours indicate a confidence level of 1$\sigma$.