Science goals

SPIRou will essentially concentrate on two main scientific goals:

  • The search for habitable exo-Earths orbiting low-mass, using high-accuracy radial velocity spectroscopic measurements. This search will expand the initial, exploratory studies being carried out now with visible instruments and will survey in particular large samples of cool stars out of reach of visible velocimeters. Carrying out a new large-scale survey at nIR wavelengths should enable to boost the sensitivity to habitable exo-Earths by typically an order of magnitude, with respect to existing instruments. SPIRou will allow, in addition, to measure the mass of transiting exoplanets that will soon be discovered by future space missions as TESS, and PLATO.

  • Expore the impact of magnetic fields on star and planet formation, by detecting magnetic fields of various types of young stellar objects and by characterizing their large-scale topologies. SPIRou will also investigate the potential presence of giant planets in the inner regions of protostellar accretion discs and their relation to disc magnetic fields. This study will strongly amplify the initial exploration survey presently carried out at optical wavelength. It will also ideally complement the data that ALMA starts collecting soon on outer accretion discs & dense prestellar cores.


    • SPIRou will also be able to tackle many other exciting research topics in stellar physics (for instance, dynamo of fully convective stars, weather patterns at the surfaces of brown dwarfs), in planetary physics (winds & chemistry of solar-system planet atmospheres), galactic physics (stellar archeology) as well as in extragalactic astronomy and cosmology.

    SPIRou challenges

    The following scientific requirements can be derived from SPIRou main science drivers:
  • The single-shot spectral domain must cover the whole 0.98-2.35 micrometer range; the K band very usefully contributes to most science programs and will be one of the unique advantages of SPIRou;
  • The resolving power must exceed 70,000;
  • The RV accuracy should be better than 1 m/s; it has implications on the stability of the instrument illumination at the entrance pinhole and on the light scrambling upstream of the spectrograph;
  • The instrument should include an achromatic, dual channel polarimeter, with swappable channels to achieve accurate and reliable polarimetry, at a precision better than 2% and sensitivity of 10 ppm;
  • The peak throughput should be ~15% from the telescope to the detector, providing a peak S/N~100 per 2 km/s pixel in 1 hr for stars of magnitude J=12 and K=11;
  • The observational efficiency must be larger than 70% for a 15 min exposure, and larger than 90% for a 1hr exposure;
  • The sky covergae must allow observing down to a zenithal distance of 70 degrees.