On March 13th, 1781 the composer, musician, and amateur astronomer William Herschel looked through his telescope and realized what he’d initially thought was a comet was, in fact, a previously unknown planet. It was the first planet discovered in modern times and, after a lot of discussion, would eventually be named Uranus, after the primordial Greek god of the sky. Although it had been observed since ancient times it was so distant and so difficult to see it was assumed to be a star. The discovery that it was a planet is why I think Uranus deserves special recognition. March 13th should be designated Uranus Day.
Uranus is distinctive in a lot of ways and, among the gas giants, can be easily overlooked. It’s not as big as Jupiter. It’s not as stormy as Neptune, although oddities in the orbit of Uranus provided clues that there was another planet beyond it, making Neptune the first planet discovered without direct observation. Although Uranus has rings they aren’t as spectacular as Saturn’s. In fact astronomers didn’t know it had rings until 1977 when, in an attempt to judge the exact size or Uranus, they watched it pass in front of a star and the star appeared to blink. With a radius of more than thirty-three thousand miles and a mass fourteen times greater than Earth you could fit a lot in Uranus.
Uranus has an axial tilt of 97.7 degrees so from Earth it appears that its rings go up and down rather than sideways. It also means that Uranus always has one pole pointed toward the sun. Astronomers think that at some point in the past a massive object slammed into Uranus, knocking it on its side. It takes Uranus eighty-four Earth years to orbit the sun, and yet Uranus spins so fast its day is just seventeen hours and fourteen minutes.
Uranus has a distinctive deep blue green color. This is because Uranus contains so much methane. Uranus has twenty-seven known moons, two of which, Titania and Oberon, are the eighth and ninth largest known moons in the solar system, and were discovered by Herschel. There’s a possibility that icy moons orbiting Jupiter and Saturn harbor life. Could there be life orbiting Uranus? It’s unlikely but that’s one of many mysteries of Uranus.
Another mystery of Uranus is whether it has a solid or liquid core. Like the other gas giants Uranus doesn’t have a solid surface, but, unlike Jupiter and Saturn its gases are icy and cold. Uranus absorbs more energy from the sun than it generates. It’s 1.84 billion miles from the sun, and it takes sunlight two hours and forty minutes to reach Uranus.
In January 1986 when Voyager 2 passed Uranus astronomers thought it was a boring planet without much going on, but the spacecraft would discover ten new moons and provide a better understanding of the rings.
And there’s still so much about Uranus we don’t know. At one time scientists thought the enormous pressures might turn carbon in Uranus’s atmosphere into giant diamonds. Now the thinking is that those pressures might produce diamonds but crush them, creating diamond rainfall. Still we don’t know whether this even happens. There’s so about Uranus to probe that I think it really is one of the most interesting planets there is, and Uranus Day is something we can all get behind.