JWST/MIRI MRS sp. of EX Lup taken in quiescence

The spectrum also shows broad emission bands from warm, submicron-size amorphous silicate grains at 10 and 18{mu}m. During the outburst, in 2008, crystalline forsterite grains were annealed in the inner disk within 1au, but their spectral signatures in the 10{mu}m silicate band later disappeared. With JWST we rediscovered these crystals via their 19.0, 20.0, and 23.5{mu}m emission, the strength of which implies that the particles are at ~3au from the star.

This suggests that crystalline grains formed in 2008 were transported outwards and now approach the water snowline, where they may be incorporated into planetesimals. Containing several key tracers of planetesimal and planet formation, EX Lup is an ideal laboratory to study the effects of variable luminosity on the planet-forming material and may provide an explanation for the observed high crystalline fraction in solar system comets.