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Pebble Drift Infographic
This graphic is an interpretation of data from Webb’s MIRI, the Mid-Infrared Instrument, which is sensitive to water vapor in disks. It shows the difference between pebble drift and water content in a compact disk versus an extended disk with rings and gaps. In the compact disk on the left, as the ice-covered pebbles drift inward toward the warmer region closer to the star, they are unimpeded. As they cross the snow line, their ice turns to vapor and provides a large amount of water to enrich the just-forming, rocky, inner planets. On the right is an extended disk with rings and gaps. As the ice-covered pebbles begin their journey inward, many become stopped by the gaps and trapped in the rings. Fewer icy pebbles are able to make it across the snow line to deliver water to the inner region of the disk.
Extended Description and Image Alt Text
Extended Description
Infographic titled “Protoplanetary Disks: Icy Pebble Drift; MIRI Medium Resolution Spectroscopy” compares the structure of a compact protoplanetary disk on the left to the structure of an extended protoplanetary disk on the right.
Both illustrations show a cross-section through the middle of the disk. The disks are angled slightly toward the viewer such that the top as well as the interior are visible. Both disks are circular, composed of a bright glowing yellow orb in the center, surrounded by concentric red rings. Above each disk is a rectangular pull-out showing a portion of the disk cross-section in more detail.
The cross-sections show that the disks vary in thickness, with the inner portions appearing thinner and denser than the outermost rings, which appear to be more cloud-like and diffuse. In both disks, dry pebbles are shown as solid brown circles and icy pebbles are shown as solid brown circles surrounded by blue rings. In both disks, icy pebbles are scattered through the outer red portions of the disk, while dry pebbles are close to the bright yellow orb. In both illustrations, there is a dashed curved line separating the icy pebbles from the dry pebbles.
In the pull-outs, this dashed line is labeled “Snow line.” The region to the right of the snow line has icy pebbles, with the far right labeled “Colder.” The region to the far left of the snow line has dry pebbles, and is labeled “Hotter.” The region in between, just to the left (warmer side) of the snow line shows brown circles with blue rings expanding outward labeled “Ice sublimation.” An arrow labeled “Drift” points toward the left: from the colder region, across the snow line, to the warmer region.
The compact disk looks continuous, with no obvious gaps between rings of red material. An arrow pointing left, from the outer edge toward the center of the disk, is labeled “Efficient drift of icy pebbles.” The pull-out is labeled “Higher water abundance” and “more icy pebbles.”
The extended disk is significantly wider and thicker than the compact disk. The disk is not continuous like the compact disk, but instead consists of two thick concentric rings of material surrounding the central bright yellow to red core. There are very distinct, wide gaps between the rings. Icy pebbles are scattered within the red ring material, but are not present in the gaps. A label below the middle ring reads “Pebbles trapped in rings.” The pull-out showing the snow line in the central region is labeled “Lower water abundance” and “Fewer icy pebbles.”
Image Alt Text
Infographic comparing pebble drift in a compact protoplanetary disk to pebble drift an extended protoplanetary disk.
- Release DateNovember 8, 2023
- Science ReleaseNASA’s Webb Findings Support Long-Proposed Process of Planet Formation
- CreditIllustration: NASA, ESA, CSA, Joseph Olmsted (STScI)
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Laura Betz
NASA’s Goddard Space Flight Center
Greenbelt, Maryland
laura.e.betz@nasa.gov
NASA, ESA, CSA, Joseph Olmsted (STScI)
