... Credit Copyright: Tom O'Donoghue Explanation: Why is the sky near Antares and Rho Ophiuchi so colorful? ... Antares , a red supergiant and one of the brighter stars in the night sky , lights up the yellow-red clouds on the lower center. Rho Ophiuchi lies at the center of the blue nebula near the top. The distant globular cluster M4 is visible just to the right of Antares , and to the lower left of the red cloud engulfing Sigma Scorpii . ... MWC 922: The Red Square Nebula . ...