Astronomy: Somewhere over the Rainbow

The Rho Ophiuchi region hosts a rainbow of colors. Credit: Adam Block, KPNO, NOAO, AURA, NSF

One of the most beautiful celestial objects for astrophotographers to capture is the Rho Ophiuchi region. This area around a star in Ophiuchus bursts with a kaleidoscope of color. The blue is the result of a reflection nebula while the red and yellow tones come from emission nebula. The white glow of the stars also contrasts with the black of thick gas and dust where light cannot penetrate.

Every color of the rainbow can be found in space, from aurora dancing at the edges of our own planet to objects millions of light years away. The colors of Rho Ophiuchi are best seen through images like the one here, but there are many objects observers can view to check out the colors of the universe. While many objects are often called red, such as Mars and the Great Red Spot, they are both more of an orangey color than true red. Nebulae are often red, such as the Lagoon Nebula, M8, in Sagittarius.

Orange belongs to the objects mentioned above, but there are plenty of other examples, including the lovely Flame Nebula. Yellow and blue are two colors that are seen best when they contrast with each other. Albireo is a double star in Cygnus that I’ve discussed here before. Another example of a yellow-and-blue object would be the galaxies in M51.

Green is a bit trickier to see. Aurorae can be green, along with the green flash of a setting sun and the bluish green tone on Uranus. As for a deep-sky object with a green hue, the Cat’s Eye Nebula is one of the best examples.

One of my favorite purplish-colored space objects is the Witch Head Nebula. All space objects tend to look less vibrant with your own eyes as compared to photographs. A confusing aspect of looking at images of space objects is that they are often photographed in false color to highlight differences that astronomers are trying to study. Therefore, the Cat’s Eye Nebula appears in one Hubble image as bright red with green tips or as a lovely blue with tinges of other colors in a different Hubble photo. But if you view the Cat’s Eye Nebula through a backyard telescope, you’ll most likely see a bluish-green nebula. Remember that everyone’s eyes are sensitive to light differently, so for some people the colorful universe can look a bit gray. 

-- Kelly Kizer Whitt loves clean, clear, and dark skies. Kelly studied English and Astronomy at the University of Wisconsin-Madison and worked for Astronomy magazine. She is currently the Feature Writer for Astronomy and Space at Suite101.com. You can follow her on Twitter at twitter.com/Astronomommy.