Uranus has a birthday

March 13, 1781, about 234 years ago, astronomer William Herschel discovered the planet Uranus.

American scientist Ellis Miner described the process in his book “Uranus: The Planet, Rings and Satellites.” Through Herschel’s telescope, it looked like a faint fuzzy spot in the sky. He knew it wasn’t a star because it moved relative to other stars each night. At first, he called it a comet, but other astronomers noticed that the “comet” did not have a tail. By observing it at several positions in the night sky, Herschel’s colleagues calculated the new object had a circular orbit out beyond Saturn. This was too far to see a comet-sized object, and they concluded Herschel had found a planet.

Herschel tried to name his discovery “Georgium Sidus,” (Latin for “George’s Planet”) after his patron King George III. The international community of astronomers disapproved the naming of a planet after the British monarch, although the British Nautical Almanac kept the name until 1850. Eventually, astronomers settled on the name Uranus, after the Greek god of the sky.

Living on Uranus would be almost impossible because it has no solid surface. The Solar System Exploration page on the NASA website describes the planet as a gas giant, like Jupiter, Saturn and Neptune. Uranus is made of thick layers of water vapor, methane and ammonia surrounding a rocky core. There is nothing astronauts could breathe in this mix; they would need technology to break down the water vapor for oxygen. There would be nothing to stand on either; astronauts would have to live in a floating habitat or on one of the 27 rocky moons.

Depending on the location of the habitat, they could have a very long day or a very long night. The planet’s axis is so tilted that it’s almost lying on its side as it orbits. When a pole is pointing at the sun, it stays in daylight while the opposite pole is dark. Uranus takes 84 Earth years to orbit the sun just once, so each pole gets 42 years of night and then 42 years of day.

Even though Uranus is a gas giant, gravity wouldn’t be a big problem for astronauts. Surface gravity on Uranus is about 10 percent less than on Earth. Uranus is more massive than Earth, so one might expect its gravity to be stronger. However, the planet is made mostly of gas, so it’s not nearly as dense as Earth. The surface is far away from the center of mass and gravity is weaker at that distance than it would be closer in.

All this shows that living on Uranus would be an interesting engineering challenge, but what NASA has learned so far through remote sensing shows it isn’t needed for science. There are no current plans for such a mission. During the 234 years since the discovery of Uranus, astronomers have studied the planet’s composition, magnetic field and weather with ground telescopes, the Voyager 2 mission and the Hubble space telescope.