Putting it together
To create the final image, Hubble’s new Wide Field Camera 3 took portraits of the Carina nebula through six filters — three in visible light and three in the infrared. All were radioed to Earth as black-and-white images, then colorized and combined into a composite.
The visible-light composite consists of snapshots taken at 673 nanometers (emission from singly ionized sulfur atoms), 657 nanometers (light from neutral hydrogen atoms) and 502 nanometers (emission from doubly ionized oxygen atoms).
Next, the NASA team gave different colors to images from each wavelength. Although both 673 nanometers and 657 nanometers fall into the red part of the spectrum, only the longest, or reddest wavelength of 673 was assigned red, while the image taken at 657 nanometers was coded green. The shortest wavelength, the emission from doubly ionized oxygen atoms, was coded in blue, the shorter end of the visible-light spectrum.
Finally, shadowing and contrast were enhanced, artifacts such as reflection halos (see second to the last image) were removed and the image was cropped to home in on the most interesting features.
Credit: NASA, ESA, and M. Livio and the Hubble 20th Anniversary Team (STScI)