Jupiter is an immense gaseous world–by far the largest planet in our Solar System–and it is about 89,000 miles wide at its equator. This true “King of Planets” is so enormous that all of the other planets in our Sun’s family could fit snugly inside of it–in fact, more than 1,000 Earths would fit inside of Jupiter! Jupiter’s huge “Great Red Spot” is considered by many scientists to be its most prominent feature, as it swirls wildly around in the surface layer of Jupiter’s banded atmosphere. In May 2014, astronomers announced that Jupiter’s famous, trademark “Great Red Spot”–which is a swirling anti-cyclonic storm larger than our own planet–has shriveled and shrunk to its smallest size ever measured!

Jupiter’s Great Shrinking Red Spot
By [http://ezinearticles.com/?expert=Judith_E_Braffman-Miller]Judith E Braffman-Miller

Jupiter is an immense gaseous world–by far the largest planet in our Solar System–and it is about 89,000 miles wide at its equator. This true “King of Planets” is so enormous that all of the other planets in our Sun’s family could fit snugly inside of it–in fact, more than 1,000 Earths would fit inside of Jupiter! Jupiter’s huge Great Red Spot is considered by many scientists to be its most prominent feature, as it swirls wildly around in the surface layer of Jupiter’s banded atmosphere. In May 2014, astronomers announced that Jupiter’s famous, trademark Great Red Spot–which is a swirling anti-cyclonic storm larger than our own planet–has shriveled and shrunk to its smallest size ever measured!

Jupiter is like a star in composition. If Jupiter had been approximately 80 times more massive than it is, it would have ignited as a fiery star–instead of becoming the enormous, gaseous planet that it certainly is!

Dr. Amy Simon of NASA’s Goddard Space Flight Center in Green Belt, Maryland, noted in the May 15, 2014 NASA Science News that recent NASA Hubble Space Telescope (HST) observations confirm the discovery that the Great Red Spot is currently about 10,250 miles across–less than 50% the size of some earlier historical measurements. Although astronomers have been watching this swirling storm since the 1600s, they didn’t notice this mysterious shrinkage until 1930.

Historic observations that date as far back as the latter part of the 19th century, measured this enormous storm to be an impressive 25,500 miles on its long axis! However, NASA’s Voyager 1 and Voyager 2 flybys of Jupiter back in 1979 measured it to be a considerably smaller 14,500 miles across. By 1995, an HST image revealed that the long axis of the swirling, stormy spot had diminished to an estimated 13,020 miles across! Even more recently, a 2009 photograph showed that the spot had shriveled down even further– to a mere 11,130 miles across!

Starting in 2012, amateur observers noticed a dramatic increase in the rate at which the spot had begun to shrivel in size. Furthermore, its shape had morphed from an oval to a circle.

“In our new observations it is apparent very small eddies are feeding into the storm. We hypothesized these may be responsible for the accelerated change by altering the internal dynamics and energy of the Great Red Spot,” Dr. Simon continued to explain.

In The Realm Of The Giant

Jupiter’s Great Red Spot is a violent storm–the largest in our Solar System. It reveals itself as a deep red blotch encircled by layers of white, pale yellow, and orange. The ferocious winds that blast around within the storm have been measured to gust at several hundreds of miles per hour, according to NASA astronomers.

Jupiter, and the lovely ringed planet Saturn, are the gas-giant duo of our Sun’s family of eight major planets–Uranus and Neptune are smaller ice-giants. This distant quartet of giant planets dwell in the outer regions of our Solar System. Both gas-giants are enormous worlds, whose secretive, hidden cores are heavily enshrouded by extraordinarily massive, dense gaseous atmospheres. Jupiter and Saturn are very different from the four, rocky inner terrestrial planets that circle our Star–Mercury, Venus, Earth, and Mars–and their weird characteristics and bewildering formation history are subjects of considerable debate within the planetary science community.

Jupiter is the fifth planet from our Sun, and its average distance from it is about 5.2 astronomical units (AU). One AU is equal to the mean distance between Earth and our Sun (which is about 93,000,000 miles), so Jupiter’s distance amounts to a little more than five times the distance between our planet and its fiery Star. When observed from Earth, Jupiter is usually the second brightest planet in the sky–after Venus. It is named after Jupiter, the King of the Roman gods.

The planet itself has been known since prehistoric times as a shining, tiny point of light in the sky. Jupiter is the fourth brightest body sparkling in the darkness of the night sky above the Earth.

Jupiter is about as big as a gas giant planet can be, and remain a planet. It is about 90% hydrogen and 10% helium–just like our Sun. But Jupiter also contains small quantities of methane, rocky material, ammonia, and water. If any more material were added to Jupiter, it would be hugged tightly by gravity, and the entire radius would increase very slightly. A star can grow to be considerably larger than Jupiter–but a star carries its own internal heat source.

When Jupiter formed in our primordial Solar System, it sparkled like a star–and, indeed, it might have become one. The energy churned out by somersaulting material caused Jupiter’s interior to become searing-hot. The more weight Jupiter gained; the hotter it grew. When the tumbling material, that was being pulled in from the encircling, swirling protoplanetary accretion disk–that danced around our Sun in its babyhood–was at long last devoured, Jupiter may well have sported an astounding diameter of more than 10 times that which it possesses today. It also had a toasty central temperature of around 50,000 Kelvin, and a glowing luminosity that was about 1% as great as that of our own Sun today.

If Jupiter had first formed considerably heavier than it did, it would have continued to grow hotter and shrink–until self-sustaining nuclear fusion reactions in its core lit its stellar fire. Had this occurred, Jupiter would have been a binary stellar companion to our Sun–and our planet and its seven sister worlds would probably have been unable to form. However, Jupiter failed. It never grew large enough to ignite, and after its sparkling birth so full of stellar promise, it began to cool down considerably.

Jupiter rotates faster than any other planet in our Solar System. One rotation–or spin–equals one day. Jupiter’s day is only about 10 Earth-hours long, and its orbit is elliptical (out-of-round, or oval). It takes Jupiter 12 Earth-years to complete one orbit around our Star, and so a year on Jupiter is equivalent to a dozen years on Earth.

The temperature in the clouds of Jupiter is a truly frigid minus 234 degrees Fahrenheit. The temperature near the planet’s center, however, is considerably hotter. Indeed, the temperature of Jupiter’s core may be around 43,000 degrees Fahrenheit. That is toastier than the surface of the Sun.

If a person could stand on the clouds at the top of Jupiter’s atmosphere–which is, of course, impossible–the force of gravity that she would be forced to endure would be approximately 2.4 times the force of gravity on the surface of the Earth. This means that a person who weighs 100 pounds on Earth would weigh about 240 pounds on Jupiter.

Jupiter is also very windy. Winds on Jupiter roar and gust at between 192 miles per hour to more than 400 miles per hour! The planet’s surface is banded with very thick red, brown, yellow, and white clouds. It also possesses three thin, gossamer rings, that were discovered in 1979 by NASA’s Voyager 1 spacecraft–and the rings are composed primarily of tiny, fine dust particles.

The magnetic field possessed by this “King of Planets” is extremely powerful. Deep down beneath Jupiter’s thick, heavy, obscuring clouds, there is an immense ocean composed of rare liquid metallic hydrogen. As Jupiter rotates, the spinning, swirling liquid metal ocean gives rise to the strongest magnetic field in our Solar System. At the tops of the clouds (tens of thousands of kilometers higher than where the field is formed), Jupiter’s magnetic field is about 20 times more powerful than the magnetic field on our own planet.

Jupiter possesses 62 known moons. The four largest moons are Io, Europa, Ganymede, and Callisto–the so-called “Galilean” moons that were named for their discoverer, Galileo Galilei, who, in 1610, was the first astronomer to peer at the Jupiter system with one of the earliest telescopes.

Since Galileo, astronomers have used newer and greatly improved telescopes on Earth to study Jupiter. In addition, they have used telescopes like the HST that orbit Earth. NASA has also dispatched spacecraft to visit the Jupiter system: Pioneer 10, Pioneer-Saturn, Voyager 1, Voyager 2, Ulysses, Galileo, Cassini and New Horizons (the Ulysses, Cassini and New Horizon spacecraft soared by Jupiter enroute to planets and locations further off in the outer limits of our Solar System). These missions observed the Jovian atmosphere, surface, moons and gossamer rings. The missions obtained up close and personal pictures of Jupiter’s strange and unique surface features.

A new spacecraft, dubbed Juno, is currently on its way to the Jupiter system. NASA’s Juno was launched in August 2011, and will reach Jupiter in 2016. The purpose of the Juno mission is to enable planetary scientists to gain a better understanding of the origin and evolution of Jupiter, and of how planets are born, in general.

Juno will orbit closer to Jupiter than any earlier spacecraft, and it will use Jupiter’s magnetic field, gravity field, and naturally occurring radio waves to study the weird and mysterious hidden interior of this heavily cloud-veiled world. Juno will also take the first images of Jupiter’s polar regions and study the enormous aurorae that light up Jupiter’s north and south poles.

Jupiter’s Great Shrinking Red Spot!

HST has been tracking the great shrinking Red Spot since entering Earth orbit back in the 1990s. As the spot shrivels, its rate of shrinkage seems to be speeding up. This accelerating shrinkage revealed to amateur astronomers in 2012 that the size of the storm had been diminishing by 580 miles per year–a bit less than the driving distance between Cincinnati and New York City.

“One possibility is that some unknown activity in the planet’s atmosphere may be draining energy and weakening the storm, causing it to shrink,” HST officials wrote in a May 15, 2014 statement to the press.

While Jupiter’s wildly raging tempest is the largest storm observed in our Solar System, it is not the only such storm. A large tempest observed on at least one other planet morphed or disappeared in recent years. A Voyager 2 image captured a Great Dark Spot blemishing the surface of the outermost planet Neptune during a 1989 flyby. However, the storm was not observed by HST when it studied the planet a decade ago.

Dr. Simon’s team plans to observe the motions of the small eddies and the internal dynamics of Jupiter’s Great Red Spot in order to determine whether these eddies either nourish or deplete momentum entering the upwelling vortex–resulting in this still unexplained shrinkage.

In 2016, when Juno reaches Jupiter, it will undertake a point-blank examination that will certainly help cast light on this mystery.

This Article Is Dedicated To Adam Michael Braffman.

Judith E. Braffman-Miller is a writer and astronomer whose articles have been published since 1981 in various magazines, newspapers, and journals. Although she has written on a variety of topics, she particularly loves writing about astronomy because it gives her the opportunity to communicate to others the many wonders of her field. Her first book, “Wisps, Ashes, and Smoke,” will be published soon.

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