I see Jupiter all the time now when walking at night. As soon as I round a corner to face east yellowy Jupiter gleams straight ahead. It’s so bright it looks bigger than all the stars. In our local cosmic neighborhood, it really is the largest thing around. If you could hollow out the planet like a Halloween pumpkin it would take more than 1,300 Earths to fill it. Although it’s currently 377 million miles (606 million km) from the Earth, Jupiter’s enormous size and perpetual cloud cover make it piercingly bright.
Contributed / NASA
Jupiter travels through the zodiac constellations just like all the other planets. Right now it’s in Aries the ram, a small group shaped like a fishing rod. Jupiter is an outer planet, meaning it orbits farther from the sun than Earth. There are five known outer planets — can you name them? The farther a planet orbits from the sun the slower it appears to move through the sky year-to-year. Since there are 12 constellations of the zodiac and Jupiter completes an orbit every 12 years it spends approximately one year in each.
Contributed / Stellarium with additions by Bob King
When you face Jupiter the next clear night take a moment to identify Aries just above it. One year from now at the same time and place, the gas giant will have departed the ram and shine instead from the horns of Taurus the bull, the next constellation to the east. All the outer planets move east through the sky as they orbit the sun. Were we to fly to Venus and look back at the Earth — an outer planet from the Venusian perspective — it would also travel eastward through the zodiac.
It’s hard to get a feel for how far Jupiter really is but let’s try. If you shot a laser beam traveling at the speed of light at the moon it would take about 1.3 seconds to arrive. Aimed at Jupiter it would take 34 minutes to complete the journey! Being far from the sun Jupiter is a very cold place. Well, at least its clouds are. That’s all we ever see of the planet — clouds. There is no solid surface. Cloud layers go down some 30 miles (50 km) before the atmosphere transitions to hydrogen and helium and then to liquified versions of these gases as density and pressure increase.
Where Jupiter’s atmospheric pressure equals the sea level pressure on Earth the temperature is 166 degrees below zero Fahrenheit (-110 degrees C). Like the Earth, the temperature rises the deeper down you go due to the enormous pressure of the overlying atmosphere as well as residual heat from the planet’s continued, slow gravitational collapse since its birth more than 4.5 billion years ago. Don’t worry. Jupiter isn’t in imminent danger of becoming a black hole. All that heat and pressure push back and keep the planet in relative equilibrium. It also lacks enough mass to crunch itself out of existence.
Contributed / Stellarium
Jupiter shows a beautiful banded appearance through a small telescope. The bands, called zones and belts, are clouds made of ammonia ice crystals mixed with water ice. Ammonia-rich air rising from the planet’s heated interior expands and cools, condensing into thick, white clouds that create the zones. Sinking air heats and evaporates the ammonia ice revealing darker, reddish-brown clouds at lower altitudes. These are the belts. Even a small scope will reveal two dark, parallel stripes called the North and South Equatorial Belts, the widest and darkest of them. Alternating east-west jet streams at the transitions between the belts and zones — blasting around 225 miles an hour (360 km/hour) — sculpt the clouds into horizontal bands.
Contributed / Christopher Go
Clouds are weather features that change form and color. With so much weather happening on Jupiter the planet’s appearance changes year to year (or sooner). You never quite know what to expect. Sometimes a belt will disappear and then return the following year or the color of the Great Red Spot morphs from peach to brick red. New storms called ovals bubble up, roll like ball bearings around the planet for a few seasons and then dissipate or merge with other clouds. Only the Great Red Spot, a giant red oval about 1.3 times the diameter of Earth, has lingered. No one is sure how long it’s been around but it may have been observed as early as the 1660s.
Jupiter has the shortest day of all the planets at around 10 hours. Breakfast at 8 a.m. and dinner at 6 p.m. would neatly cover one full Jovian rotation. The fifth planet is also rich with moons of which 95 are known. Four are bright enough to see in binoculars or a small telescope. Early next month when Jupiter will be closest to Earth I’ll post a special feature on the moons and how to spot them.
“Astro” Bob King is a freelance writer and retired photographer for the Duluth News Tribune. You can reach him at [email protected].
