Do Extrasolar Planets Have Comet Belts?

Question of the week: Dr. Ross, do we know if other planetary systems have the equivalent of Kuiper Belts or Oort clouds of comets and asteroids, and what might this indicate about fine-tuning?

My answer: Astronomers are able to detect comet and asteroid belts around other planetary systems. They typically do so by searching for the dust that would inevitably result from occasional collisions among the comets and asteroids. I have written about these observations in my book, Improbable Planet, and provide an update and more detail in my book, Designed to the Core.

Most planetary systems that have been observed don’t possess comet or asteroid belts. Those that do, possess asteroid and comet belts at least hundreds of times larger than those in the solar system. I explain in the two books how the sizes and migration histories of a planetary system’s gas giant planets determine the existence and characteristic features of the planetary system’s asteroid and comet belts. The solar system’s asteroid and comet belts are unique, owing to the unique features of the Sun’s gas giant planets. The solar system’s asteroid and comet belts must possess exactly the features that they do for advanced life to be possible on Earth.