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 .
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