Image Description


This image spans the boundary between the constellations Ophiuchus and Scorpius.  The bright yellow star at upper-left is Alpha Scorpii or Antares.  Blue reflection nebulae extend along the constellation boundary from the star Iota Scorpii to Rho Ophiuchi.  The red emission nebula at image bottom surrounds star Sigma Scorpii.  Two globular star clusters are located along the left edge of the image.  Both these clusters are much more distant than most of the stars or nebulae.
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Reflection nebulae are cold interstellar clouds of dust and gas which reflect light of nearby stars.  Red light passes through or is absorbed by these cold clouds while blue light is scattered or reflected consequently, they usually appear blue in astrophotos.  Emission nebulae are hot clouds of gasses, mostly hydrogen, which fluoresce with a red light when illuminated by ultraviolet radiation from nearby stars.  The yellow cloud around Antares is a combination of both types.