What do you think of this fact?
Humans have known about Neptune since 1846. In all that time, the planet has managed exactly one lap around the Sun. It finished it in 2011.
Found with a pen before a telescope
Neptune is the first planet that was located through mathematical predictions, according to NASA. Astronomers had noticed that Uranus wasn’t moving quite the way it should. Something unseen seemed to be tugging at it. In the mid-1840s, the French mathematician Urbain Le Verrier and John Couch Adams from England each worked out independently where that mystery planet had to be.
Le Verrier sent his numbers to Johann Galle at the Berlin Observatory. On September 23, 1846, Galle looked at the predicted spot and found Neptune. A planet found on paper first, then in the sky.
One year, 165 years long
Neptune sits about 30 times farther from the Sun than Earth does, so it is in no hurry. One orbit takes about 165 Earth years, or 60,190 Earth days. On July 12, 2011, Neptune completed its first full orbit since Galle found it.
Its days are the opposite story: one Neptune day, a single spin on its axis, lasts only about 16 hours. The first spacecraft to fly past it was NASA’s Voyager 2, in 1989.
Bonus fact: Galileo saw Neptune long before anyone discovered it. In December 1612 and January 1613 he recorded it, but took it for a star and never realized it was a planet.
So if Neptune celebrated birthdays, it would have had exactly one since we met it, and the next one is due around 2176.