Three examples of the combination of red, green, and blue filtered grayscale images into one of color using the technique I described previously.
When a star similar to our sun reaches the end of its life, it blows off the material near the surface in a colorful “last hurrah” nebula. The grayscale images I used for this picture were taken on Feb. 6, 2007, by the Hubble Space Telescope. See their color image. The outer layers of gas had formed a cocoon around the star core. Ultraviolet light from the star now makes the debris glow. Different colors indicate elements of hydrogen, helium, oxygen, nitrogen, etc. The white dot burned-out star in the center is called a white dwarf. Our sun will do the same in about 5 billion years. Follow this link to a short video describing the location in Puppis southeast of Sirius and Orion. Click images to embiggen.
This is a fun one called the Eskimo Nebula for obvious reasons. It looks like a furry parka around a face. It is found in the constellation Gemini northeast of Sirius and Orion. It is another of the many examples of nebulae found around expired sun-like stars in our galactic neighborhood. See the APoD image from Hubble.
There are many examples of galaxies undergoing various stages of collision in the universe. This pair is in the early stages. Neither has been disrupted by the gravitational pull of the other yet. The smaller one on the right is a little in the background. They original image I saw for these came from APoD in November 2004. That image placed them at the correct distance apart. I could only find grayscale images of them as separate galaxies on the Hubble site. In order to place them near each other at the correct distance, I needed to leave some black space. I like the effect anyway.