On this date in 1846, the planet Neptune was discovered by Urbain Le Verrier and John Couch Adams, then verified by Johann Galle. Galileo (the philosopher-mathematician-astronomer, not the spacecraft that orbited Jupiter) may actually have seen it more than two hundred years earlier, but he mistook it for a star. Additional controversy surrounded whether the Frenchman and the Brit should really share credit for the discovery, and recent assessment leans toward Le Verrier doing the more significant work.
Between 1930 and 2006, Pluto held the title of farthest planet from the Sun. Pluto was discovered by Clyde Tombough, who was born in Streator, Illinois, and later worked at the Lowell Observatory in Arizona. But Pluto was reclassified because it never cleared the neighborhood of its own orbit, and few were more devastated than the residents of Streator. In other words, it didn’t have enough planetary gravitas and doesn’t push and pull other objects in its orbital neighborhood. Neptune not only celebrates its discovery day today, but last week it celebrated the five-year anniversary of its return to ascendancy as the farthest planet from the Sun.
The eighth planet was named by its discoverer, Le Verrier, after the Roman god of the sea. The planet has thirteen moons. Neptune is seventeen times heavier than the Earth, has high surface gravity, and takes almost 165 years to orbit the Sun. None of us on Earth will live through a complete Neptune orbit. Imagine if each season lasted 40 years. What’s really mind-boggling when you think about time and how we measure it by the Earth’s rotation (a day) and orbit (a year) is that, because Neptune isn’t solid like the Earth, its equator takes about two hours longer to rotate than its poles, 18 hours and 16.1 hours, respectively.
Some of what we know about Neptune and many of the images we have of it—photos of its rings, its dark spots (storms)—are a result of the flyby of Voyager 2 in 1989. PBS based Neptune All Night on that spacecraft flyby. According to NASA, 11,000 workyears were devoted to Voyager 1 and 2 through the Neptune flyby; that’s equivalent to one-third of the work effort devoted to building the Great Pyramid at Giza. These spacecraft each carry a disc, the Golden Record, of 115 images and also many sounds, including greetings in 55 languages, chosen by Carl Sagan and his team, just in case Voyager runs into anybody else out there. Antennas are still tracking these spacecraft as they move farther and farther away, now into the Heliosheath. In fact, in 1998, Voyager 1 passed Pioneer 10 to become the spacecraft to travel farthest from Earth.
Okay, so maybe it’s not exactly the eight planet’s birthday, but discovery is worth celebrating. Unfortunately, Neptune can never be seen with the naked eye, but a telescope or even binoculars can help us make it out in the night sky. Click HERE for some information about peeking at Neptune this fall.