In 2006 the International Astronomical Union officially defined the wordplanet reclassifying Pluto as a dwarf planet. Each updated title in this setreflects the... » 

In 2006 the International Astronomical Union officially defined the wordplanet reclassifying Pluto as a dwarf planet. Each updated title in this setreflects the change while the Pluto title explains what a dwarf planet is anddescribes how the decision was made. Stay current with these revised editions «