In addition to overruling the International Astronomical Union (IAU)’s demotion of the planet (at least within the state), the unanimously-approved bill also designated March 13, 2009 as “Pluto Day,” since Illinois’ own Clyde Tombaugh discovered Pluto on that date in 1930.
Pluto was downgraded to a dwarf planet in 2006, because it didn’t meet the requirement that a planet clear the area around it of debris due to its gravity. Ever since the IAU’s diss, many people—including astronomers, other state legislators, and ordinary citizens—have criticized the organization’s definition of a planet, which was formulated by only 424 of 2,412 IAU astronomers. The IAU subsequently decided to show Pluto some love by classifying it and all dwarf planets beyond Neptune’s orbit as “plutoids.”
Stay tuned on Discovermagazine.com for a recap of an astronomy roundtable that included Mike Brown, whose discovery of Eris (a dwarf planet larger than Pluto) delivered Pluto’s planetary death blow.
Bad Astronomy: Pluto’s big Hill to climb
Bad Astronomy: Sharpest image of Pluto ever taken
80beats: The Fourth Dwarf Planet Is Officially Christened: Meet “Makemake”