An Icy Disk in the Orion Nebula

Silhouetted against the background glow of the Orion Nebula, the protoplanetary disk 114–426 provides an excellent opportunity to study a site of planet formation. The discovery of water ice in this disk suggests that ice can survive in disks in the dense star cluster environments where most stars form.

Clues to Our Planetary Past

To understand how our solar system came to be, researchers can search for clues close to home, piecing together the compositional and dynamical hints that persist today — or they can look farther afield, taking cues from distant young planetary systems in the throes of formation.

Protoplanetary disks — disks of gas and dust that encircle young stars and set the stage for planet formation — provide an opportunity to understand how our solar system may have formed. In today’s article, JWST provides a new perspective on an unusual protoplanetary disk.

A Disk’s Silhouette

The Orion Nebula is a prolific star-forming region that’s home to hundreds of young stars. At the nebula’s center is the Trapezium Cluster, a tight-knit grouping of massive stars that illuminates the surrounding nebula. Located near the Trapezium Cluster, the protoplanetary disk 114–426 (named according to its coordinates) is notable for both its size and its location. At more than 1,000 au across — about 25 times the distance from the Sun to Pluto — it’s one of the largest disks in the region. It’s also oriented edge-on from our perspective, showing off a narrow disk of gas and dust that is illuminated from behind by the bright glow of the Orion Nebula.

Previous observations of 114–426 with the Hubble Space Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA) allowed for detailed studies of the dust grains in the disk. Now, Nicholas Ballering (Space Science Institute and University of Virginia) and collaborators have used JWST’s Near Infrared Camera to scan the disk in 12 wavelength bands from 1 to 5 microns (1 micron = 10^-6 meter).

The JWST observations showcase 114–426’s edge-on, dusty disk and two bright lobes of scattered light from the hidden star at the disk’s center. The two lobes are asymmetrical, which previous research suggests means that the inner part of the disk is tilted. A tilted disk could mean that the hidden central star is actually a binary system, or that the star is orbited by a massive planet.

Icy Interpretation

Looking at the portions of the disk that extend beyond the lobes of scattered light, Ballering’s team identified several wavelengths where the spectrum dips, indicating absorption of the background light. One such feature around 3 microns is due to water ice, which has been identified in other protoplanetary disks.

The team estimated that about half an Earth mass of ice and dust is present in the areas of the disk that are backlit by the Orion Nebula. Given that this disk is subjected to intense ultraviolet radiation from the nearby Trapezium Cluster, it may seem surprising that water ice can survive there. However, the team’s calculations showed that the disk is far too cold for ice to sublimate, and the ultraviolet radiation from nearby stars isn’t sufficient to remove the ice from the surface of dust grains.

This finding suggests that water ice is likely to survive in disks around stars in cluster environments like this one. The fact that ice persists is important for planet formation, as ice helps dust grains clump together into pebbles and eventually planets. Ice may also play a role in the transport of water from the cold outer regions of disks to the temperate inner regions where habitable planets may reside.

Citation

“Water Ice in the Edge-On Orion Silhouette Disk 114–426 from JWST NIRCam Images,” Nicholas P. Ballering et al 2025 ApJ 979 110. doi:10.3847/1538-4357/ad9b7a