Close-up view: Protoplanetary Disc in Taurus Molecular Cloud | LDN 1551 | Webb
Herbig-Haro objects are small nebulae found in star formation regions, marking the locations where gas outflowing from young stars is heated into luminescence by shockwaves. HH 30 is an example of where this outflowing gas takes the form of a narrow jet. The source star is located on one end of the jet, hidden behind an edge-on protoplanetary disc that the star is illuminating.
HH 30 is of particular interest to astronomers. In fact, the HH 30 disc is considered the prototype of an edge-on disc, thanks to its early discovery with the NASA/European Space Agency Hubble Space Telescope. Discs seen from this view are a unique laboratory to study the settling and drift of dust grains.
An international team of astronomers have used Webb to investigate the target in unprecedented detail. By combining Webb’s observations with those from the Hubble Space Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA), the team was able to study the multiwavelength disc appearance of the system.
The long-wavelength data from ALMA trace the location of millimeter-sized dust grains. These are found in a narrow region in the central plane of the disc. The shorter-wavelength infrared data from Webb reveal the distribution of smaller dust grains. These grains are only one millionth of a meter across—about the size of a single bacterium. While the large dust grains are concentrated in the densest parts of the disc, the small grains are much more widespread.
These Webb observations were taken as part of the Webb GO program #2562 (PI F. Ménard, K. Stapelfeldt). It aims to understand how dust evolves in edge-on discs like HH 30. Combined with the keen radio-wavelength eyes of ALMA, these observations show that large dust grains must migrate within the disc and settle in a thin layer. The creation of a narrow, dense layer of dust is an important stage in the process of planet formation. In this dense region, dust grains clump together to form pebbles and eventually planets themselves.
In addition to the behavior of dust grains, the Webb, Hubble, and ALMA images reveal several distinct structures that are nested within one another. Emerging at a 90-degree angle from the narrow central disc is a high-velocity jet of gas. The narrow jet is surrounded by a wider, cone-shaped outflow. Enclosing the conical outflow is a wide nebula that reflects the light from the young star that is embedded within the disc. Together, these data reveal HH 30 to be a dynamic place, where tiny dust grains and massive jets alike play a role in the formation of new planets.
Image Description: A close-in image of a protoplanetary disc around a newly formed star. Many wavelengths of light are combined and represented by separate and various colors. A dark line across the center is the disc, corresponding to the densest parts of the disc, made of opaque dust: the star is hidden in here and creates a strong glow in the center. A band going straight up is a jet, while other outflows above and below the disc, and a tail coming off to one side.
Release Date: Feb. 4, 2025
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