Reflection nebula IC 4604, optical image. IC 4604 is the name given to the large reflection nebula surrounding the central triple star called Rho Ophiuchi (centre). These gas and dust clouds do not produce their own light but reflect the light of adjacent stars. The light is blue because blue light is scattered more than red light. IC 4604 forms part of the Rho Ophiuchi/Antares nebula complex, one of the most colourful regions of the sky. It lies about 500 light years from Earth in the constellation Ophiuchus and north of Antares (Alpha Scorpii, not shown), the brightest star in the constellation Scorpius. Image taken using the Canada-France-Hawaii Telescope, Mauna Kea, Hawaii, USA.