young stellar object
- A protostar in which the dust and gas have collapsed into a sufficiently massive body for fusion to begin. The characteristic trait of young stellar objects is the presence of jet outflows-either of molecular gas or of radioactive emissions-that interact with the interstellar medium out of which the star has just been born. See more at protostar.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.