[Paper Review] Using SPICA Space Telescope to characterize Exoplanets

J. R. Goicoechea, B. Swinyard+27 more|ArXiv.org|Sep 1, 2008

Astronomy and Astrophysical Research2 references3 citations

TL;DR

This white paper proposes that the SPICA space telescope, a Japanese-led JAXA-ESA mission with a cryogenically cooled 3.5m mirror, will enable high-sensitivity mid- and far-infrared observations to characterize exoplanet atmospheres. It demonstrates SPICA’s capability to directly detect and spectroscopically analyze Jupiter- and Neptune-sized planets at >5–10 AU and to study transiting super-Earths down to 1–2 Earth radii via high-resolution spectroscopy and multiband photometry.

ABSTRACT

We present the 3.5m SPICA space telescope, a proposed Japanese-led JAXA-ESA mission scheduled for launch around 2017. The actively cooled (<5 K), single aperture telescope and monolithic mirror will operate from ~3.5 to ~210 um and will provide superb sensitivity in the mid- and far-IR spectral domain (better than JWST at lambda > 18 um). SPICA is one of the few space missions selected to go to the next stage of ESA's Cosmic Vision 2015-2025 selection process. In this White Paper we present the main specifications of the three instruments currently baselined for SPICA: a mid-infrared (MIR) coronagraph (~3.5 to ~27 um) with photometric and spectral capabilities (R~200), a MIR wide-field camera and high resolution spectrometer (R~30,000), and a far-infrared (FIR ~30 to ~210 um) imaging spectrometer - SAFARI - led by a European consortium. We discuss their capabilities in the context of MIR direct observations of exo-planets (EPs) and multiband photometry/high resolution spectroscopy observations of transiting exo-planets. We conclude that SPICA will be able to characterize the atmospheres of transiting exo-planets down to the super-Earth size previously detected by ground- or space-based observatories. It will also directly detect and characterize Jupiter/Neptune-size planets orbiting at larger separation from their parent star (>5-10 AU), by performing quantitative atmospheric spectroscopy and studying proto-planetary and debris disks. In addition, SPICA will be a scientific and technological precursor for future, more ambitious, IR space missions for exo-planet direct detection as it will, for example, quantify the prevalence exo-zodiacal clouds in planetary systems and test coronographic techniques, cryogenic systems and lightweight, high quality telescopes. (abridged)

Motivation & Objective

• To assess SPICA’s potential for characterizing exoplanet atmospheres in the mid- and far-infrared domain.
• To evaluate SPICA’s capabilities for direct detection and spectroscopic analysis of exoplanets at large orbital separations (>5–10 AU).
• To investigate SPICA’s role in studying proto-planetary and debris disks around young stars.
• To determine SPICA’s technological and scientific readiness as a precursor for future, more advanced infrared exoplanet missions.
• To quantify the prevalence of exo-zodiacal dust clouds in planetary systems using SPICA’s coronographic and cryogenic systems.

Proposed method

• Utilize SPICA’s actively cooled (<5 K) single-aperture telescope operating from 3.5 to 210 µm to achieve superior sensitivity in the mid- and far-infrared compared to JWST at longer wavelengths.
• Deploy three baseline instruments: a mid-infrared coronagraph (3.5–27 µm, R ~ 200), a mid-infrared wide-field camera and high-resolution spectrometer (R ~ 30,000), and the far-infrared imaging spectrometer SAFARI (30–210 µm).
• Conduct direct imaging of exoplanets using coronographic techniques to suppress starlight and enable detection of faint planetary signals.
• Perform high-resolution spectroscopy of transiting exoplanets to retrieve atmospheric composition, temperature profiles, and cloud properties.
• Use multiband photometry and spectroscopy to analyze atmospheric features in transmission and thermal emission for transiting super-Earths.
• Quantify exo-zodiacal dust levels by observing thermal emission from circumstellar dust disks and testing coronagraphic performance.

Experimental results

Research questions

• RQ1 Can SPICA detect and characterize the atmospheres of transiting exoplanets down to super-Earth size (1–2 R⊕) in the mid-infrared domain?
• RQ2 What is the sensitivity of SPICA to directly detect and spectroscopically analyze gas giants and ice giants at orbital separations greater than 5–10 AU?
• RQ3 To what extent can SPICA resolve and characterize the thermal emission and composition of proto-planetary and debris disks around young stars?
• RQ4 How prevalent are exo-zodiacal dust clouds in planetary systems, and can SPICA provide statistical constraints on their distribution and density?
• RQ5 To what degree can SPICA serve as a technological and scientific precursor for future direct exoplanet detection missions in the infrared?

Key findings

• SPICA will achieve better than JWST sensitivity at wavelengths longer than 18 µm, enabling high-sensitivity observations in the mid- and far-infrared domain.
• The telescope will be capable of detecting and characterizing transiting exoplanets down to super-Earth size (1–2 R⊕) via high-resolution spectroscopy and multiband photometry.
• SPICA can directly detect and perform quantitative atmospheric spectroscopy on Jupiter- and Neptune-sized exoplanets at orbital separations exceeding 5–10 AU.
• The mission will enable detailed study of proto-planetary and debris disks through high-sensitivity imaging and spectroscopy in the far-infrared.
• SPICA will quantify the prevalence of exo-zodiacal dust clouds in planetary systems, providing critical data for future direct imaging missions.
• The mission will test and validate key technologies such as advanced coronagraphy, cryogenic systems, and lightweight, high-quality monolithic mirrors for future infrared space telescopes.