Credit: NASA/HST/NOAO

Visible-light images of the Trifid taken with NASA's Hubble Space Telescope, Baltimore, Md. (inset) and the National Optical Astronomy Observatory, Tucson, Ariz., (background image) show a murky cloud lined with dark trails of dust. Data of this same region from the Institute for Radioastronomy millimeter telescope in Spain revealed four dense knots, or cores, of dust, which are "incubators" for embryonic stars. Astronomers thought these cores were not yet ripe for stars, until Spitzer spotted the warmth of rapidly growing massive embryos tucked inside.