Arcturus, the brightest star in the constellation Botes and one of the brightest stars in the night sky. Arcturus is a giant orange-colored star with a diameter about 25 times that of the sun. The surface temperature of Arcturus is only 7,000 F. (3,870 C.), some 3,000 F. (1,670 C.) less than the sun's surface temperature. Because of its size, however, Arcturus gives off more than 100 times as much light and heat as the sun. Arcturus is approximately 36 light-years from the earth. It has an apparent magnitude of -0.1 and an absolute magnitude of -0.3.
Asteroid belts aren't quite the dense fields of gigantic spinning rocks that you may have seen in a "Star Wars" film, but they're still fascinating. In fact, the main asteroid belt may tell us how our entire solar system came into existence.
Sunspots are peculiar dark areas that show up regularly on the surface of the sun -- and often for no reason. What causes them? What effect could these funny little spots have on the Earth?