The James Webb Space Telescope has captured two protoplanetary discs — Tau 042021 in Taurus and Oph 163131 in Ophiuchus, located 450 and 480 light-years away respectively. Both images were selected as ESA/Webb's Picture of the Month.
What makes these observations exceptional is their geometry: both discs are oriented edge-on toward us, with the bright young stars at their centres almost entirely hidden behind layers of dust. This allowed Webb's NIRCam and MIRI instruments to reveal the finest dust particles lifted above the disc midplane, glowing in reflected starlight and forming structures that resemble colourful spinning tops against the black of space. The range of colours from red to green maps varying grain sizes, as well as the presence of hydrogen, carbon monoxide, and polycyclic aromatic hydrocarbons.
For Oph 163131, Webb and Hubble data are complemented by observations from ALMA, which detects much larger, millimetre-sized grains concentrated in the disc's central plane — exactly where conditions are right for grains to clump together and build planetesimals. Strikingly, ALMA has also revealed a gap in the disc's inner ring, a likely sign of a planet already carving out its orbit. This is the same process that, billions of years ago, gave rise to our own Solar System.