Figure 2-22 RIVUXG Creating an Artificial “Star” A laser beam shines upward from Gemini North Observatory, near the summit of Mauna Kea on the island of Hawaii. The beam strikes sodium atoms that lie about 56 mi (90 km) above Earth’s surface, causing them to glow and make an artificial “star.” Tracking the twinkling of this “star” makes it possible to undo the effects of atmospheric turbulence on telescope images.