Seventy-two protoplanetary disks, swirling cocoons of cosmic dust and gas, came under the gaze of the MIRI instrument on JWST. Most of them shoot outflows into space: dense conical structures and narrow, high-speed jets. They blast like fountains. This process is not accidental. It carries away excess angular momentum, without which material cannot fall onto the star. The birth of future exoplanets directly depends on how long and how strongly such a fountain operates.

As the disk ages, the fountain's appearance changes dramatically. While accretion is rapid (more than 10⁻⁸ solar masses per year), about 80% of disks eject dense molecular winds and swift jets. Neon atoms are accelerated in them to speeds exceeding 30 km/s, reliably detected via Doppler shift. When the flow of material onto the star weakens, the picture becomes completely different: dense molecular cones vanish, leaving only a faint atomic breeze. Winds also slow planetary migration, preventing planets from falling onto the star. Such a transition from a vigorous fountain to calm evaporation has been traced statistically for the first time.

The evolution from a molecular fountain to atomic evaporation fits perfectly into plasma physics described by Maxwell's equations. At early stages, dense gas cocoons shield the star's harsh radiation, and jets are confined by magnetic fields. When accretion subsides and shielding drops, X-rays and ultraviolet break through and trigger photoevaporation — gas removal by light. This process gives rise to atomic winds, gradually eroding the disk. The cosmic fountain first churns with dense jets, then transitions to barely noticeable evaporation, leaving behind a mature planetary system.

Future measurements will allow estimation of how much mass winds carry away at each stage and compare these losses with theory. This will let us read the full history of quieting fountains around young stars, sites of star formation, and the birth of worlds like our own.