Figure 11-12 A Young Star Cluster and Its H-R Diagram (a) Newborn stars, hidden behind thick dust, are revealed in this image of the NGC 2264 from NASA’s Spitzer Space Telescope. These infant stars appear to have formed in regularly spaced intervals along linear structures in a configuration like the pattern of a snowflake. The youngest protostars form straight lines and have yet to scatter from their location of formation. (b) Each dot plotted on this H-R diagram represents a star in NGC 2264, whose luminosity and surface temperature have been determined. This star cluster probably started forming only 2 million years ago.