<text><span class="style10">he Outer Planets (3 of 6)</span><span class="style7"></span><span class="style10">Neptune</span><span class="style7">Neptune is so distant that it can never be seen with the naked eye and even a small telescope will only show it as a tiny disc. Larger telescopes show that the planet is bluish-green in color, but very few markings can be seen. Our first good look at Neptune came in August 1989, when the </span><span class="style26">Voyager 2</span><span class="style7"> spacecraft flew past the planet. </span><span class="style26">Voyager</span><span class="style7"> revealed Neptune's most prominent feature, the Great Dark Spot. This is a massive storm system in the planet's atmosphere and is similar to Jupiter's Great Red Spot. Small wispy white clouds of methane ice can also be seen circling the planet.The outside layer of Neptune is made of the gases hydrogen and helium. Beneath this comes a layer of ice. The ice is made of frozen methane and ammonia, as well as frozen water. At the center of the planet is a rocky core.Neptune was discovered thanks to the mathematical calculations of two men. They were an Englishman, John Couch Adams (1819-92), and Urbain Le Verrier (1811-77) from France. Adams and Le Verrier had been looking at the movements of Uranus and had noticed that it was behaving in a very strange manner. Sometimes it would speed up and move quickly along its orbit, whereas at other times it would slow down. The two men both thought that Uranus was being pulled by the gravity of another planet, so they set out to calculate where the `hidden planet' must be. Both men worked on their own, but they eventually arrived at the same answer. Le Verrier sent details of his calculations to the observatory in Berlin. The German astronomers Johann Galle (1812-1910) and Heinrich d'Arrest (1822-75) looked for the planet in September 1846 and found it almost immediately.Neptune is now known to have eight satellites and a system of four rings Triton is the largest of Neptune's satellites, with a diameter of 2270 km (1410 mi) - slightly smaller than that of the Earth's Moon. Triton has an atmosphere and its surface is covered with a frozen mixture of nitrogen and methane.</span></text>
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<text><span class="style10">eptune and its Great Dark Spot</span><span class="style7"> photographed through colored filters by </span><span class="style26">Voyager 2</span><span class="style7"> in August 1989 from a distance of 6.1 million km (3.8 million mi). The Great Dark Spot is a giant storm system the size of the Earth.</span></text>
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<text>ΓÇó THE SUN AND THE SOLAR SYSTEMΓÇó THE INNER PLANETSΓÇó THE HISTORY OF ASTRONOMYΓÇó SPACE EXPLORATION</text>
