Webb unveils evolving dust system and energetic jets
Herbig-Haro objects, like HH 30, appear as luminous markers in star-forming regions. Their glow comes from gas heated by shockwaves as it streams from young stars. In HH 30, a narrow jet emerges from the star itself, which remains hidden behind the edge-on disc it illuminates.
Astronomers have a particular interest in HH 30. Hubble Space Telescope observations first identified it as a prototypical edge-on disc, a vantage point that provides a rare way to study how dust particles drift and settle within these young planetary systems.
An international collaboration harnessed Webb's powerful view, together with data from the Hubble Space Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA), to examine this system's multiwavelength characteristics. ALMA's longer-wavelength data track millimetre-sized dust grains, confined to a thin band in the disc's central plane. Meanwhile, Webb's infrared measurements reveal the spread of far smaller grains - only about a millionth of a meter across - distributed much more widely.
As part of Webb GO programme #2562 (PI F. Menard, K. Stapelfeldt), these observations highlight how large dust grains migrate inward and collect into a narrow layer. Such clustering is a critical milestone in planet formation, where dust grains fuse into pebbles and eventually merge into fully fledged planets.
Beyond dust evolution, Webb, Hubble, and ALMA data uncover multiple nested structures in HH 30. A high-speed jet shoots out at a right angle to the thin disc, encircled by a cone-shaped outflow. A broader nebula envelops the cone, reflecting light from the young star. Together, these elements paint a picture of a dynamic system, where tiny particles and imposing jets help shape the creation of new worlds.
Research Report:JWST Imaging of Edge-on Protoplanetary Disks. IV. Mid-infrared Dust Scattering in the HH 30 disk
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