Beautiful and mysterious, peaceful and serene, the moon is the brightest object in the night sky. Jupiter and Saturn have more than sixty moons each. Neptune has thirteen moons. Even Mars has two moons. But the Earth, our planet, only has one moon, our nearest neighbor in space. Even though the moon is close to us when compared to other planets, it is still very, very far away. The moon is about 239 thousand miles or 384 thousand kilometers away. You would have to travel all the way around the Earth nine and a half times to go the same distance as the space between the Earth and the Moon. The moon is much smaller than the Earth. Ifthe Earth was hollow, about fifty moons could fit inside. Because it is so much smaller than the Earth, the moon's gravity is much weaker. This means that if you were to visit the moon, you would weigh much less than you do on earth, only about 1/6th of your current weight. That means that if a giraffe was on...
When Pluto was discovered in 1930, it was named the ninth planet of the solar system. More than seventy-five years later, that planetary status was revoked and Pluto was demoted to a dwarf planet. Many people were left wondering what changed,and what the difference was between a planet and a dwarf planet.
The controversy began in 1992 when astronomers discovered other icy bodies out beyond Neptune's orbit, in a region called the Kuiper Belt. The debate only intensified when objects approaching Pluto's size were discovered. In 2005, an object called Eris was discovered,which appeared to be larger than Pluto. Some people wanted Eris recognized as the tenth planet.
Others argued that so many objects similar to Pluto in the same area of space meant that Pluto was not a planet, but some new kind of object. In 2006, the International Astronomical Unionformed a committee to decide once and for all what characteristics qualified an object to be called a planet.
According to the committee, a planet must orbit around the Sun, have enough mass to pull itself into a round or nearly round shape, and have cleared its orbit of other objects and debris. Pluto met the first two guidelines, but notthe third, meaning it could not be considered a planet.
The term dwarf planet was created for objects that orbit the Sun and have enough mass to pull themselves into mostly round shapes, but have not cleared their orbits of other objects. Currently, five objects in the solar systemare classified as dwarf planets – Pluto, Eris, Ceres, Haumea, and Makemake – and it is likely that more will be discovered.
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