On the synergetic use of Ariel and JWST for exoplanet atmospheric science

TL;DR

The paper investigates strategic synergies between JWST and Ariel for exoplanet atmospheric science, highlighting how their complementary designs enable broader target access, time-domain studies, and joint observing opportunities. By comparing capabilities, identifying shared science questions, and outlining pre-launch and in-operation coordination pathways, it demonstrates how JWST’s high-SNR, high-resolution data can inform Ariel’s large-survey approach and how Ariel can broaden JWST’s contextual and population-wide insights. Key contributions include a framework for targeting, observing strategies (including time-intensive phase-curves and simultaneous observations), and scenarios illustrating how combined data can address planetary formation, atmospheric chemistry, and habitability across diverse exoplanets. The study argues that coordinated use of both observatories will maximize scientific returns, guide observing programs, and set a template for multi-mission exoplanet exploration into the 2030s and beyond.

Abstract

This paper explores the potential for strategic synergies between the JWST and the Ariel telescopes, two flagship observatories poised to revolutionise the study of exoplanet atmospheres. Both telescopes have the potential to address common fundamental questions about exoplanets-especially concerning their nature and origins-and serve a growing scientific community. With their operations now anticipated to overlap, starting from 2030, there is a unique opportunity to enhance the scientific outputs of both observatories through coordinated efforts. In this report, authored by the Ariel-JWST Synergy Working Group, part of the Ariel Consortium Science Team, we summarise the capabilities of JWST and Ariel; we highlight their key differences, similarities, synergies, and distinctive strengths. Ariel is designed to conduct a broad survey of exoplanet atmospheres but remains highly flexible, allowing the mission to integrate insights from JWST's discoveries. Findings from JWST, including data from initiatives shaped by NASA's decadal survey priorities and community-driven research themes, will inform the development of Ariel's core survey strategy. Conversely, Ariel's ability to perform broad-wavelength coverage observations for bright targets provides complementary avenues for exoplanet researchers, particularly those interested in time-domain observations and large-scale atmospheric studies. This paper identifies key pathways for fostering JWST-Ariel synergies, many of which can be initiated even before Ariel's launch. Leveraging their complementary designs and scopes, JWST and Ariel can jointly address fundamental questions about the nature, formation, and evolution of exoplanets. Such strategic collaboration has the potential to maximise the scientific returns of both observatories and lay the foundation for future facilities in the roadmap to exoplanet exploration.

Figures (9)

• Figure 1: Ariel mission profile. Left: example of a possible Ariel target list for the primary mission (4 years) overlayed over JWST Cycle 1-4 exoplanets; Right: available targets satisfying the Ariel core survey (i.e., Tier 2). Over the primary mission, Ariel should obtain primary transits and secondary eclipses at Tier 2 quality (see example of Tier 2 data quality in Figure \ref{['fig:telescope_characteristics']}) for about 500 exoplanets---spanning a wide range of planetary radii and temperatures. TPC: TESS Planetary Candidates. The figure is inspired by edwards_ariel2, which offers more details on Ariel targets.
• Figure 2: Comparative view of the key performances of the JWST's instruments and Ariel for transiting exoplanets. Top table summarises the characteristics of instruments and observing modes for JWST. Central left panel: simulations of a WASP-39 b-like exoplanet, used as example of a relatively faint target ($V_\mathrm{mag}\sim$ 12) optimal for various JWST's instruments (NIRSpec, NIRISS, MIRI) and observable by Ariel in Tier 2 (2 transits). Bottom left panel: simulation of a HD189733 b-like exoplanet, used as example of a bright target ($V_\mathrm{mag}\sim$ 7.7) observable with JWST NIRCam and optimal for Ariel in Tier 3 (1 transit). JWST's noise is obtained with the ExoCTK Pandexo tool Batalha_2017, while the Ariel's noise is estimated using the ArielRad simulator.
• Figure 3: Summary of JWST observations in cycles 1 to 4. The different panels indicate the instruments used (NIRISS, NIRSpec, NIRCam, or MIRI), while the colors code the observing techniques. Black dots: all currently known exoplanets; blue dots: transit observations; red dots: eclipses, green dots: phase-curves. Note: NIRCam includes F322W2, and F444W; NIRSpec-Grisms include G235M, G235H, G395M, and G395H; MIRI filters include FW1280W, and FW1500W.
• Figure 4: Ariel target candidates plotted as a function of planetary temperature and stellar brightness (J mag). The size of the datapoints is proportional to the planetary radius. Colours indicate the required number of transit or eclipse events per target to reach Ariel's Tier 2 data quality. Targets in the shaded area are observable with NIRSpec-PRISM. For transit observations, brightness and planetary size are the key discriminant between Ariel and JWST; for eclipse observations, it is rather brightness and planetary temperature.
• Figure 5: Simulations of phase-curves as observed by Ariel. Left panels: phase-curves; middle panels: eclipse spectra; right panels: thermal profiles with solid lines for the sub-stellar point and dashed line for the anti-stellar point. Panel A: hot-rocky exoplanet inspired from 55-Cnc e. The planet has a secondary atmosphere (99% CO + 1% CO$_2$, from Hu_2024) and a radius $\sim 2.0 \, R_{\oplus}$. Panel B: sub-Neptune inspired from LTT-9779 b with a 1000x metallicity atmosphere Hoyer_2023. We assumed $R_p \sim 4.7 \, R_{\oplus}$.