EVEN as you mourn Pluto’s demise as a planet, spare a thought for Ceres. Twice in as many centuries astronomers have fought for the asteroid to be listed as a planet. Twice they have failed.
By 1800, astronomers were convinced an undiscovered world lay between Mars and Jupiter. The belief had been building since 1781, when the maverick English astronomer William Herschel discovered Uranus. It seemed to confirm a numerical law governing the distances of the planets. Now known as the Titius-Bode law, this also predicted a planet between Mars and Jupiter.
Then, on 1 January 1801, working at his…
