Icy comets inherit crystalline silicates from stellar furnaces during protostar outbursts.

JWST observations of the periodically bursting protostar EC 53 detected crystalline silicates (forsterite and enstatite) appearing during accretion outbursts. The team reports that thermal annealing in the hot inner disk and layered magnetohydrodynamic winds could carry those crystals outward toward comet-forming zones.

Young stars can heat and reshape the dust around them. New observations using the James Webb Space Telescope focused on EC 53, a protostar about 1,400 light-years away that brightens on a regular cycle. During EC 53's accretion outbursts the team detected specific crystalline silicates forming in the inner disk. The researchers report that strong, layered disk winds at the same time could lift and move those crystals outward to the colder, comet-forming regions. Key findings: - JWST spectra of EC 53 showed forsterite and enstatite appearing during accretion bursts and not between bursts. - The emergence of these spectral features is reported as evidence of thermal annealing in the hot inner disk where temperatures exceed about 900 K. - Observations revealed strong, layered outflows and magnetohydrodynamic (MHD) disk winds that could uplift small crystalline grains and transport them outward. - EC 53 is known to enter roughly 100-day long outbursts approximately every 18 months, episodes of rapid accretion and enhanced winds. - The authors caution that whether crystals survive the journey and reach the outer disk efficiently is not fully established and remains speculative. Summary: The study provides direct observations that crystalline silicates can form in the hot inner region of a young star's disk during burst phases and that disk winds offer a plausible route for outward transport. This mechanism helps explain why crystals appear in comets and implies the proto-Sun may have experienced similar events early in the Solar System's history. How often crystals survive and are delivered to the comet-forming zone is undetermined at this time.