If you haven’t noticed Jupiter the past few weeks, your skies are even cloudier than mine. The solar system’s biggest planet is now at opposition and closest to the Earth for the year. Closest also means biggest and brightest. Look up the next clear night and let your eyes be drawn to a vivid light in the east. Yes, that’s the bad boy we’re talking about.
Opposition – when an outer planet lines up on the same side of the sun as our own – happens when Earth laps the planet. For Jupiter, this happens very 13 months. Mars takes about two years to reach opposition, because it orbits much closer to the sun and move so quickly, Earth needs extra time to catch up.
Jupiter’s orbit isn’t a perfect circle but slightly oblong, so the distance between it and Earth at each opposition varies over a period of about 12 years. Earth and Jupiter were closest in 2010 and have been gradually separating since. We’ll have to wait until 2021 until we’re this close again, making 2012-13 the best time to observe the planet for the next 9 years.
Since planets at opposition are opposite the sun in the sky, Jupiter rises at sunset in the constellation Taurus the Bull and remains visible all night long. Only when the sun rises again, does the planet slip below the western horizon for some shuteye.
That’s plenty of time to use binoculars to spot up to four of its brightest moons snugged up on either side of the planet. Highlights for those with telescopes include the two rusty-red stripes on either side of Jupiter’s midsection. Called the North and South Equatorial Belts or NEB and SEB, they remind me muddy tire tracks. Careful study will reveal the narrower North and South Temperate Belts parallel to their equatorial cousins. And if the air is steady enough to allow magnifications of 100x or higher, you might even catch a glimpse of the Great Red Spot (GRS), a pale red-orange “eye” located in a hollow just south of the SEB.
Jupiter is the color planet. On good nights, I can see dirty reds in the equatorial belts, shades of gray and brown in the temperate belts, hints of orange sherbet in the GRS and occasional yellow shades in the lighter zones that separate the belts.
All these shades are due to the presence of chemical compounds containing elements like sulfur and phosphorus in clouds composed of ammonia ice crystals.
Multiple jet streams with winds blasting up to 325 mph alternate eastward to westward with latitude and streamline the clouds into the stripes or belts that give Jupiter its distinctive bumble bee look.
Jupiter’s rapid rotation rate of just 9.8 hours helps drive the fierce winds and also flattens the planet out like a chef spinning a ball of pizza dough. With no solid surface, it spins fast enough to stretch out into an oval more than 6,000 miles wider at its equator than pole to pole. Look closely and you can’t miss Jupiter’s squashed appearance through the telescope.
No matter how you take your cup of Jupiter, whether by naked eye or sweetened with binoculars or telescope, the view is always rewarding.