Top: The quantity age/10¹⁰ yr as a function of the disk‐to‐star luminosity ratio, τ, corresponding to a rough estimate of the occurrence of microlensing events of circumstellar disk systems. Bottom: The required exposure time to detect the disk (gray lines) and to detect a 10% change in the disk flux (solid black lines) at the 3 σ level with the JWST. The thin and thick solid lines are computed for reemitted light at 15 and 25.5 μm, respectively, and include noise contributions from the instrument self‐emission and the zodiacal light. The dashed line corresponds to the microlensing signal seen from the reflected light of the disk at 2 μm, for which the main source of noise comes from the star light.