The Colorful Clouds of Rho Ophiuchi
From NASA’s Astronomy Picture of the Day
The many spectacular colors of the Rho 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 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.
The red and yellow 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 brown regions are
caused by dust grains -
born in young stellar atmospheres - which effectively block light emitted
behind them.
The Rho Ophiuchi star clouds,
well in front of the globular
cluster M4 visible above on lower left, are even
more colorful than humans
can see - the clouds emits light in every wavelength
band from the radio to
the gamma-ray.
