Mars, which is the fourth planet from the sun and the third smallest in size, got its name because of its rusty red color. People associated the planet's blood-red color with war, so they named it Mars, after the Roman god of war.
Why does the moon look so much bigger when it is near the horizon than when it is high up in the sky? This question has been pondered for hundreds if not thousands of years, and is commonly referred to as the moon illusion. See more »
Ganymede, a satellite of the planet Jupiter. With a diameter of 3,270 miles (5,260 km), Ganymede is the largest satellite in the solar system, and is larger than the planet Mercury. See more »
Kuiper Belt, a disk-shaped region of space, extending beyond the orbit of Neptune, in which a very large number of minor planets are in orbit around the sun. See more »
Sun, the star at the center of the solar system. Like other stars, the sun is a huge, hot, gaseous sphere. See more »
Solar rays and the potential problems they may cause are explained in this article. Learn about solar rays. See more »
