Antares and Rho Ophiuchi
Why is the sky near Antares and Rho Ophiuchi so colorful? The colors result from a mixture of objects and processes. Fine dust illuminated from the front by starlight produces blue reflection nebulae . Gaseous clouds whose atoms are excited by ultraviolet starlight produce reddish emission nebulae . Backlit dust clouds block starlight and so appear dark . Antares , a red supergiant and one of the brighter stars in the night sky , lights up the yellow-red clouds on the upper left. Rho Ophiuchi lies at the center of the blue nebula on the right. The distant globular cluster M4 is visible just below Antares , and to the left of the red cloud engulfing Sigma Scorpii . These star clouds are even more colorful than humans can see, emitting light across the electromagnetic spectrum .