However, every time I have ever learned about the planets from 3rd grade on, Pluto was ALWAYS the “Exception.” IE, “All the outer plannets are large and gassious, well, except for pluto.” “All the planets are on the same plane and orbit the sun in the same direction, well, except for pluto, whose orbit is perpendicular and backwards from all the others.”

At least to my childhood mind it always felt like if Pluto is an exception to every other rule we know about the plannets, then it ISN’T a planet. But again, that’s the ramblings of a childhood mind… And I guess only 4% of the leading astronomer organization agree, so maybe I’m entirely off base.

The Illinois legislature has way more sense than the International Astronomical Union has shown in two-and-a-half years. It’s the IAU who have acted like idiots, with one tiny group forcing a nonsensical planet definition on everyone. The truth is there is NO scientific consensus that Pluto is not a planet. The criterion requiring that a planet “clear the neighborhood of its orbit” is not only controversial; it’s so vague as to be meaningless. Only four percent of the IAU even voted on this, and the vote was driven by internal politics. A small group, most of whom are not planetary scientists, wanted to arbitrarily limit the number of planets to only the largest bodies in the solar system. They held their vote on the last day of a two-week conference with no absentee voting allowed. Their decision was immediately opposed by hundreds of professional astronomers in a formal petition led by Dr. Alan Stern, Principal Investigator of NASA’s New Horizons mission to Pluto.

Stern and like-minded scientists favor a broader definition of planet that includes any non-self-luminous spheroidal body orbiting a star. The spherical part is key because when objects become large enough, they are shaped by gravity, which pulls them into a round shape, rather than by chemical bonds. This is true of planets and not of shapeless asteroids and comets. And yes, it does make Ceres, Eris, Haumea, and Makemake planets as well, for a total of 13 planets in our solar system.

Even now, many astronomers and lay people are working to overturn the IAU demotion or are ignoring it altogether. Kudos to the Illinois Senate for standing up to this closed, out of touch organization whose leadership thinks they can just issue a decree and change reality.