It saddens me that my children will grow up seeing only eight planets on the posters at school, whereas I grew up with nine. As of August 2006, Pluto has been classified as a dwarf planet. RTB astrophysicist Jeff Zweerink isn’t as sentimental as I am about Pluto—he understands and appreciates the reasons for the former planet’s demotion.

The discovery of the Kuiper belt brought Pluto’s qualifications as a planet into question. Since 1992, astronomers have cataloged more than 1,000 objects of substantial size occupying the region beyond Neptune. As an occupant of that region, Pluto is considered a member of the Kuiper belt.

This region helps answer a young-earth challenge to the old-earth view, namely the source of comets. It’s known that one class of comets is short-lived—yet we still see them in our solar system. Young-earth creationists argue that this circumstance indicates the solar system is far younger than scientists believe. How else can we account for the appearance of short-lived comets in our cosmic neighborhood?

The Kuiper belt provides an alternative explanation. Astronomers believe this object field comprises the source of the short-period comets that visit our planetary neighborhood. Thus, our solar system contains a mechanism for supplying short-period comets and asteroids, which have supplied Earth with water and other life-essential elements, despite being billions of years old.

Still, some in the young-earth camp have questioned the Kuiper belts’ supply of comet-sized objects. RTB physicist Dave Rogstad reports on research that answers these challenges.

Pluto may be exiled from the planet club, but as a member of the Kuiper belt it looks like it’s still in good company.

— Maureen

Resources: Asteroids and comets played an important role in preparing Earth for advanced life. Search “bombardment” on the RTB website to get the details.