Entry for September 03, 2007/ Colorful Astronomy Picture for Labor Day

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2007 September 3

The Colorful Clouds of Rho Ophiuchi
Credit:Adam Block,KPNO Visitor Program,NOAO,AURA,NSF

Explanation:The many spectacular colors of theRho Ophiuchi (oh'-fee-yu-kee) clouds highlight the many processes that occur there. The blue regions shine primarily by reflected light. Blue light from the starRho Ophiuchi and nearby starsreflects more efficiently off this portion of the nebula than red light. The Earth'sdaytime sky appears blue for the same reason. The red and yellow regions shine primarily because ofemission from the nebula's atomic and molecular gas. Light from nearby blue stars - more energetic than the bright starAntares - knockselectrons away from the gas, which then shines when the electrons recombine with the gas. Thedark regions are caused bydust grains - born in young stellar atmospheres - which effectively block light emitted behind them. TheRho Ophiuchi star clouds, well in front of theglobular clusterM4 visibleabove on far lower left, are even more colorful thanhumans can see - the clouds emits light in everywavelength band from theradio to thegamma-ray.

Tomorrow's picture:martian crater