It’s been rainy and overcast for several days now, but over the weekend the clouds finally broke up, the sun came out, and in the mornings Venus has been bright in the southeast. This morning I noticed something almost as bright underneath it: Jupiter. Jupiter is the fourth brightest object in the night sky, after the Sun, Moon, and Venus, which always makes me wonder, why did ancient astronomers call it Jupiter? How did they know it was the biggest planet in the solar system? Venus is brighter, and closer, which makes it appear closer. Jupiter is so large some astronomers think it’s really a failed star–which kind of makes sense since it’s really a big ball of mostly hydrogen and helium, with no solid surface, which seriously undermines the plot of Clifford D. Simak’s Desertion, although it does make sense that the climax of Arthur C. Clarke’s 2010 revolves around Jupiter becoming a second sun in our solar system even though in his novel 2001, unlike the movie, the ill-fated Discovery One heads to Saturn, but that’s another story.
Jupiter spins around the Sun taking almost twelve years at a time to make a full orbit. Ancient Chinese astronomers associated it with prosperity, and Babylonians associated it with their god Marduk who gradually rose to become top of the pantheon.
And it’s got that big swirling red spot, a hurricane so large Earth could fit into it three times, that was definitely first seen in 1831, but may have first been spotted in 1664 and there have been signs it might be clearing up but somehow it just keeps going. Then there are Jupiter’s moons–at least seventy-nine. The four largest, Europa, Ganymede, Io, and Callisto, were first seen by Galileo, who started the tradition of naming them after Jupiter’s lovers, and luckily for astronomers the Roman god, and his Greek counterpart, got around a lot, and more than five hundred years later we’re still learning new things about them. Europa’s ice may hide life, and just last month astronomers got pictures of a volcano erupting on Io, which is the most active moon in the solar system.
Anyway, after a lot of digging I could only figure that it was just dumb luck that the biggest planet in the solar system just happens to be named Jupiter. And in an interesting astronomical coincidence about twelve hours later, hanging in the same part of the sky, was Sirius, the brightest star in the night sky.