From the October 2018 issue

Juno’s planetary past

Though once considered a full-sized planet, the third asteroid ever discovered faced demotion long ago.
By | Published: October 19, 2018 | Last updated on May 18, 2023

few months ago, we were privy to a close opposition of Mars — an event that occurs all too infrequently. This month, we set our sights on another favorable but uncommon opposition of a planet: Juno.

“Wait a second,” you protest. “Juno isn’t a planet!” Actually, it was — two centuries ago. 

Here’s the story. By the end of the 18th century, the distances from the Sun to the known planets seemed to obey a mathematical sequence as proposed by Johann Titius and Johann Bode. But there was a glitch: No planet existed between Mars and Jupiter, where Bode’s law predicted one should be. Then, on the very first day of 1801, Italian astronomer Giuseppe Piazzi discovered a body, later named Ceres, in the prescribed location. The solar system was complete, according to Bode’s law.

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