RIVUXG Stars appear to rotate around Polaris, the North Star (top), in this time exposure, taken January 26, 2006. Below Polaris is the 4-m telescope dome at Kitt Peak National Observatory near Tucson, Arizona. The image is composed of 114 thirty-second exposures of the night sky combined to make the equivalent of a nearly 1-hour exposure in which Earth’s rotation causes the stars to appear to move across the night sky. The orange glow on the horizon is from the city of Phoenix, 160 km (100 mi) away.