© by Zane B. Stein
WHAT ARE THE CENTAURS?
CENTAURS - LIKE A RAINBOW
One of the most interesting things about Centaur, aside from their orbits, is their range of colors. True, many of them are a dull grey, but Chiron is blue or blue-grey, there are some that are blue-green, and Pholus is rust-red.
What is the reason for the variation in colors? While it was originally thought that all the Centaurs were escapees from the Kuiper Belt, there is growing evidence that not all of them came from the same place. Some of them may actually have been ejected from the gas giant planets. As you may know, Neptune has a greenish color, Uranus blue, Saturn pale yellow and Jupiter a rusty red. More and more, it is looking like the color of many Centaurs point to their birth from one of the other planets in our solar system. And there is even some evidence that Saturn's moon Phoebe may once have been a Centaur that was captured by Saturn's gravitational pull.
Another reason for the color differences may be that the Centaurs are made up of different materials, or at least, their surface chemicals are different. Thus Pholus' red color may be due to a high percentage of organic material.
Here is a grid showing the range of Centaur colors, matching them up against the colors of Mars, and two of Saturn's Moons:
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