That brilliant star? It’s Jupiter, now at its closest to us until two more presidential terms have come and gone.
As a result, it’s extremely bright – and out all night long. Simply look around. It’s nicely up after 7 p.m. or so, some three times brighter than the Dog Star Sirius, the most luminous true star. Another way to confirm – say, around 9 p.m. – is to follow Orion’s belt. The belt points down and left to bluish Sirius. It points up and right to yellow-white Jupiter.
This planet changed Galileo’s life. After he’d heard that a Dutch eyeglass-maker had invented the first telescope two years earlier, Galileo was one of the few people who, sight unseen, could duplicate the instrument, and demonstrated it to a merchant organization in Venice as a way to discover when ships were approaching ahead of anyone else.
Galileo then turned his telescope to the sky. Instantly the universe changed. The Moon – regarded since ancient Greek times as a smooth body with oceans – was dramatically pockmarked with mountains and craters. The Milky Way’s creamy glow burst into untold separate stars. The Sun, considered a featureless object, had spots whose changing positions showed that it rotated. Wonder upon wonder!
But it was Jupiter, shining brilliantly in Taurus in January of 1610, that proved the most amazing. On the 7th, the 46-year-old Galileo saw three “stars” lined up alongside the planet. By the 13th he had watched them change position each night, spotted a fourth as well and realized that they were orbiting that world.
This was no small thing. At the time, Church doctrine placed Earth at the center of all motion. That here was another planet around which several other bodies circled degraded Earth’s status. The stage was set for a life-or-death drama. As it turned out, Galileo gained no personal benefits after he published his startling discoveries. Instead it brought him up on charges, forced him to recant at penalty of being burned at the stake, got him placed under permanent house arrest and left him to die penniless.
Since then, Jupiter has orbited the Sun 34 times and now again hovers in that same constellation of Taurus. Even a $50 telescope lets us clearly observe the giant world and its four huge moons, now named the Galilean Satellites in his honor. Today’s worst instruments far exceed Galileo’s best 30x telescope, because back in 1610 no one had yet figured out how to get rid of the false smudgy color that plagued the early optics.
Jupiter is large enough to swallow up 1,100 Planet Earths. It spins faster than any other planet, creating horizontal cloud formations like stripes on a bumblebee. The spin is a little faster at the equator than at the poles, so gaseous boundary layers brush past each other, producing violent eddies, curlicues, swirls, white spots and of course the famous Red Spot, a permanent hurricane three times the size of Earth.
Jupiter shows far more detail though amateur telescopes than any other planet, though a steady night when stars are not twinkling is vital to perceiving intricate features. But while we’re looking, we might take a moment to salute the first person who marveled at its wonders, on that night 402 years ago.
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