This image of the sky around bright stars Antares (Alpha Scorpii) and Rho Ophiuchi (oh'-fee-yu-kee) reveals spectacular colors in a cosmic starscape. Near the top, blue light from the star Rho Ophiuchi and nearby stars reflects more efficiently off this portion of the nebula than red light. The Earth's daytime sky appears blue for the same reason. Cool supergiant star Antares (near the center) is itself shedding the material that reflects the evolved star's yellowish hue. The red regions shine primarily because of emission from the nebula's atomic and molecular gas. Light from nearby blue stars - more energetic than the bright star Antares - knocks electrons away from the gas, which then shines when the electrons recombine with the gas. The dark regions are caused by dust grains - born in young stellar atmospheres - which effectively block light emitted behind them. About 500 light-years away, the Rho Ophiuchi star clouds, are well in front of the nearby globular star cluster M4, visible just below and right of center (text adapted from APOD). Pentax SDHF75+RC0.72x35 - SBIG STL11K - L (60m) RGB (20m each) - Meeline Station, Mt. Magnet, Western Australia
Double, double toil and trouble; Fire burn, and cauldron bubble -- maybe Macbeth should have consulted the Witch Head Nebula. This suggestively shaped reflection nebula on the lower left is associated with the bright star Rigel, to its right, in the constellation Orion. More formally known as IC 2118, the Witch Head Nebula glows primarily by light reflected from Rigel. Fine dust in the nebula reflects the light. Pictured above, the blue color of the Witch Head Nebula and of the dust surrounding Rigel is caused not only by Rigel's blue color but because the dust grains reflect blue light more efficiently than red. The same physical process causes Earth's daytime sky to appear blue, although the scatterers in Earth's atmosphere are molecules of nitrogen and oxygen. Rigel, the Witch Head Nebula, and gas and dust that surrounds them lie about 800 light-years away (text adapted from APOD). Pentax 67 EDIF 300mm f/4 - FLI Proline 16803 - Ha (180m) L (150m) R (40m) G (40m) B (40m) - Warrumbungle Observatory, Coonabarabran, NSW, Australia
