science -- October 2, 2013 at 3:55 PM ET
Live chat on the rise of dwarf planets
When astronomer Mike Brown announced "Pluto is dead" during a 2006 press conference at Caltech, he sent science teachers and publishers scrambling to alter textbooks and classroom displays. Brown, the author of How I Killed Pluto and Why It Had It Coming, had discovered another planet-like object, nicknamed Xena, that was larger than Pluto. And Xena wasn't a planet either.
Scientists decided that a planet must be in orbit around a star, but itself not be a star. It must be large enough for its own gravity to pull it into a nearly spherical shape and have "cleared the neighborhood around its orbit." Pluto is disqualified because its oblong orbit overlaps with Neptune and instead is placed into the "dwarf planet" category.
Brown and science writer Brad Hooker will host a live chat to discuss the discovery and what dwarf planets mean to science today. The chat begins at 4 p.m. EDT Wednesday. Follow below and submit your own questions.