Emission nebula IC 4606. True-color optical image of the emission nebula IC 4606 (center left) and other assorted nebulae in the constellations Scorpius and Ophiuchus. IC 4606 surrounds the red giant star Antares (Alpha Scorpii). This nebula is lit up by ionization of its hydrogen gas by radiation from the star. To the right of Antares is the globular star cluster M4 (NGC 6121). At upper center is the blue reflection nebula IC 4604, which reflects the light of the star Rho Ophiuchi (top center). At center right is the star Sigma Scorpii, which is also surrounded by red nebulosity.