The many faces of HH 30

This new NASA/ESA/CSA James Webb Space Telescope Picture of the Month presents HH 30 in unprecedented resolution, complementing observations from the NASA/ESA Hubble Space Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA). This target is an edge-on protoplanetary disc that is surrounded by jets and a disc wind, and is located in the dark cloud LDN 1551 in the Taurus Molecular Cloud. 

Herbig-Haro objects, like HH 30, are luminous regions surrounding newborn stars (known as protostars). They form when stellar winds or jets of gas spewing from these newborn stars form shockwaves as they collide with nearby gas and dust at high speeds.

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 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 Hubble and ALMA, the team was able to study the multiwavelength disc appearance of the system. 

The four smaller images on the left show HH 30 as it appears at visible, near-infrared, millimetre, and mid-infrared wavelengths. The larger image on the right combines data from Webb’s Near-InfraRed Camera (NIRCam) and Mid-InfraRed Instrument (MIRI). The submillimetre image from ALMA, which shows the location of millimetre-sized dust grains, is dramatically different from the infrared and visible-light perspectives from Webb and Hubble. While the Webb and Hubble observations reveal delicate structures that extend into space, the ALMA observations show that the large dust grains are narrowly concentrated in the central plane of the disc.

These Webb observations were taken as part of the Webb GO programme #2562 (PI F. Ménard, K. Stapelfeldt), which 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 behaviour 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 collage of four small and one large images of protoplanetary disc HH 30, from different telescopes and in various colours representing different wavelengths of light. Each displays different features of the disc and the outflows around it. They are labelled (top to bottom and left to right) “Hubble/Visible”, “Webb/Near-infrared”, “Webb/Mid-infrared”, “ALMA/Millimetre”, and (the large one) “Webb/Infrared”.]

Links

• Science paper
• Webb image of HH 30
• Annotated image of HH 30’s features