Proplyd

A protoplanetary disk surrounding a young star, often seen as an ionized envelope or tail shaped by ultraviolet radiation from nearby massive stars.

Photoevaporation: The loss of gas from a surface when radiation heats it enough to escape as a flow. Ultraviolet heating drives gas off the disk and forms its outward-flowing envelope.
Orion Nebula: A nearby star-forming nebula containing young stars, ionized gas, and dense molecular material. Its bright central region hosts the most familiar population of proplyds.
C. R. O'Dell: An American astronomer known for research on the Orion Nebula and planetary nebulae. O'Dell helped identify the compact protoplanetary structures in the Orion Nebula.
Disk lifetime: The duration for which a young star retains its circumstellar disk. External photoevaporation can shorten a proplyd’s disk lifetime.
H II region: A region of ionized hydrogen surrounding hot stars that emit ultraviolet radiation. Many observed proplyds sit inside the Orion Nebula’s ionized H II region.
Theta1 Orionis C: A massive O-type star in the Orion Trapezium and a major source of ultraviolet radiation. Its radiation illuminates and erodes many proplyds in the Orion Nebula.
Bruce A. Wen: An astronomer who coauthored the early report identifying compact sources in the Orion Nebula. Wen and O'Dell’s 1993 study established the observational class later called proplyds.
Planet formation: The growth of planets from gas, dust, and solid bodies orbiting a young star. Disk erosion can reduce the material and time available to form planets.
Ionization front: A boundary where ionizing radiation changes neutral gas into ionized gas. It marks where radiation from nearby massive stars ionizes gas flowing from a proplyd.
Orion Trapezium Cluster: A compact group of massive young stars at the center of the Orion Nebula. Its intense radiation field creates the environment in which Orion proplyds are observed.

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