Pluto Demoted: No Longer a Planet
The International Astronomical Union voted on August 24, 2006, to reclassify Pluto as a "dwarf planet," stripping it of the planetary status it had held since Clyde Tombaugh discovered it in 1930. The decision was driven by the discovery of Eris, a trans-Neptunian object slightly more massive than Pluto, which forced astronomers to either accept dozens of new planets or create a stricter definition. The new criteria required a planet to have "cleared its orbital neighborhood," which Pluto, sharing the Kuiper Belt with thousands of similar objects, had not done. Only 424 of the IAU's roughly 10,000 members voted, and the decision provoked public outrage, particularly in New Mexico, where the state legislature declared that Pluto would always be a planet within its borders.
August 24, 2006
20 years ago
Key Figures & Places
What Else Happened on August 24
Gaius Scribonius Curio crossed into Africa in 49 BC with two legions, chasing Pompey's allies, certain he had the upper hand. He didn't. Publius Attius Varus ha…
Mount Vesuvius erupted on August 24, 79 AD, burying the Roman cities of Pompeii and Herculaneum under roughly 20 feet of volcanic ash and pumice. Pliny the Youn…
Valentinian I elevated his eight-year-old son Gratian to the rank of co-Augustus, formalizing a dynastic succession plan to secure the imperial throne. This mov…
The last known inscription in Egyptian hieroglyphs was carved at the Temple of Isis on the island of Philae in 394 AD, a dedication by a priest named Esmet-Akho…
Alaric I and his Visigoth forces breached the Salarian Gate, initiating the first sack of Rome in eight centuries. This collapse of the city’s perceived invulne…
Vandal king Genseric led his forces into Rome in 455 AD, and Pope Leo I negotiated a deal: no killing, no burning, in exchange for the gates being opened. The V…
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