Jupiter is the first of the outer planets (also known as gas giants) is found 5 AU from the Sun. Jupiter is the largest planet in the Solar System and has a diameter 11 times the diameter of Earth and takes 12 years to orbit the Sun once. The Great Red Spot is a storm on the surface of the planet that is the size of Earth and has been churning for hundreds of years. The cause for this hurricane-like storm is not clearly understood. Jupiter has over 30 moons. The 4 largest moons are Io, Europa, Ganymede (largest moon in the Solar System) and Callisto. These 4 moons are easily visible with a good pair of binoculars or small telescope. Europa is of great interest at this time because it is thought to have vast oceans of water beneath its thick covering of ice. Io is the most volcanically active body in the Solar System.

Saturn is the next stop on our tour of the gas giants. Although having over 60 moons, the most notable feature of the planet is its stunning rings. These rings are made up of tiny ice particles that reflect the Sun’s light very effectively and they too, are visible with good quality optics. However, one of the moons, Enceladus is also thought to have liquid water beneath its ice-covered surface. Slightly smaller than Jupiter, Saturn is almost 10 times the size of Earth. Lying 10 AU from the sun it takes 30 years to orbit the Sun.

The last two planets in the Solar System are Uranus (pronounced Ur – a – nus) and Neptune. These 2 are significantly smaller than Jupiter and Saturn and are found at 20 and 30 AU from the Sun, respectively. Because of their great distance from the Sun it takes a long, long time for them to orbit the Sun. It takes Uranus 84 years to orbit the Sun and Neptune takes a whopping 165 years. The most unique feature of Uranus is that it is tilted so that its poles are pointed toward the Sun.

Regrettably for some, Pluto is no longer considered a planet. It is now classified as a “dwarf planet”. More on that and other bodies in the Solar System in the next article.

Please feel free to contact me at mwyatt@comancheisd.net if you have any questions. I may not know the answer, but I will try my best to find it. I will respond to your email and hope to be able to post your question and the answer in the Chief.

Marty Wyatt

Astronomy Teacher, Comanche High School

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