In the 1840s, astronomers were sure another planet was tugging on Uranus causing it to move differently than predicted. They soon discovered Neptune. Mercury also moved differently than predicted. Naturally, they thought another planet must be tugging on it too. Briefly, they thought they found it. Continue reading →
¡SkyCaramba! Weekly astronomy blog for the week ending March 29, 2014
In the 1500s and 1600s, astronomers grew increasingly certain that Earth and the other planets go around the sun. By the early 1700s, mathematics could predict the planets’ positions fairly accurately using a sun-centered model. But in the 1840s, the best observers found that Mercury didn’t move exactly as predicted.
In 1846, astronomer Urbain Le Verrier figured out why Uranus also moved differently than expected. Another planet’s gravity tugged on it. His mathematical analysis led to Neptune’s discovery. Astronomers were sure another planet must be tugging on Mercury. Since nobody ever saw it, they thought it must orbit closer to the sun than Mercury which itself is somewhat hard to see. They hoped to discover it someday when it passed in front of the sun.
One day, someone did see something cross the sun’s disk. A French physician and amateur ...