Facts About Jupiter and the Missing Stripe
Jupiter is the largest planet in the solar system with a diameter of 88,846 miles (142,984 kilometers), which is more than 11 times that of Earth and about one-tenth that of the sun. Jupiter is usually the second brightest planet after Venus, but occasionally Mars is brighter for a few weeks. Jupiter is the fifth planet from the sun with an average distance from the Sun of about 483,780,000 miles (778,570,000 kilometers), or about five times Earth's distance from the Sun. The planet completes one orbit in 4,333 Earth days, or almost 12 Earth years.
When observed through a telescope, Jupiter is dominated by two dark bands in its atmosphere, with one in the northern hemisphere and one in the southern hemisphere. The most recent images taken by astronomers have revealed the lower stripe known as the Southern Equatorial Belt has disappeared leaving the southern half of the planet bare. The band was seen at the end of last year before Jupiter moved behind the Sun on its orbit. When it emerged three months later the belt had disappeared.
It is not the first time this unusual phenomenon has been noticed. Jupiter loses or regains one of its belts every ten of 15 years, although exactly why this happens is a mystery. The color and intensity of the belts and regions varies over time and the Southern Equatorial Belt was fading slightly last year.
Jupiter’s complex belt system
The planet is a giant ball of gas and liquid with a solid core of unknown size. It's surface is composed of dense red, brown, yellow, and white clouds arranged in lighter areas called zones and darker regions called belts.
These clouds are created by chemicals that have formed at different heights. The highest white clouds in the zones are made of crystals of frozen ammonia. Darker, lower clouds are created from chemicals including sulfur and phosphorus. The clouds are blown into bands by high winds of over 350 mph caused by Jupiter's rapid rotation.
Jupiter rotates faster than any other planet as it only takes 9 hours 56 minutes to spin around once on its axis, compared with 24 hours for Earth. Scientists cannot measure the rotation of the interior of the giant planet directly, so they have calculated the speed from indirect measurements. Jupiter sends out radio waves strong enough to be picked up by radio telescopes on Earth. Scientists can now measure these waves to calculate Jupiter's rotational speed. The strength of the waves varies under the influence of Jupiter's magnetic field in a pattern that repeats every 9 hours 56 minutes. Because the magnetic field originates in Jupiter's core, this variation shows how fast the plant's interior spins.
Jupiter is heavier than any other planet. Its mass (quantity of matter) is 318 times larger than that of Earth. Although Jupiter has a large mass, it has a relatively low density. Its density averages 1.33 grams per cubic centimeter which is slightly more than that of water. The density of Jupiter is about 1/4 that of Earth. Because of Jupiter's low density, astronomers believe that the planet consists primarily of hydrogen and helium. Jupiter's mix of chemical elements resembles that of the Sun and belongs to the class of planets often referred to as “Gas Giants.”
Jupiter will be closest to Earth on September 24, offering stargazers their best chance of seeing it without its stripe.