A ring of dust around young stars where planets may form.A dust ring is a circumstellar disk of fine particles and gas orbiting a young star, often marking the region where planet formation takes place. These rings are the raw material reservoirs from which planets coalesce over millions of years. They appear as bright or dark bands in infrared and millimeter observations, tracing the distribution of dust that will eventually clump into planetesimals and protoplanets.
The concept of circumstellar dust disks was established in the 1980s with the discovery of excess infrared emission around Vega and other stars, interpreted as dusty debris. The first direct images of dust rings around young stars came from the Hubble Space Telescope in the 1990s.
Dust rings form from the collapse of a molecular cloud into a rotating protostar. Conservation of angular momentum flattens the infalling material into a disk, where dust grains collide and stick together, growing into larger bodies. The ring structure often emerges from gaps carved by nascent planets, or from pressure bumps that trap dust particles, preventing them from drifting inward.
Dust ring observations guide the search for exoplanets and inform models of planetary system formation, helping astronomers identify stars likely to host forming planets.
The dust ring around the star HL Tauri, imaged by ALMA in 2014, shows gaps so sharply defined that they imply the presence of young planets still embedded in the disk.
| r_H | variable | Hill sphere radius — length metre |
| a | variable | semi-major axis — length metre |
| m | variable | mass of the smaller body — mass kilogram |
| M | variable | mass of the central body — mass kilogram |
| ∛ | operator | cube root operation — cube root |



























