How asteroids lost their planethood | Astronomy.com

For 150 years, scientists considered asteroids to be planets. What made them reconsider?

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Mark Sykes ,Giuseppi Piazzi ,William Herschel ,Pierre Simon Laplace ,Philip Metzger ,James Hilton ,Alan Stern ,Kirby Runyon ,Immanuel Kant ,International Astronomical Union ,Titius Bode Law ,