Testing Gemini’s Super-Laser

This image shows Gemini North, one half of the International Gemini Observatory, operated by NSF NOIRLab, using a yellow-colored laser beam to adjust its adaptive optics system during commissioning in 2016. This laser emanates from the middle of the telescope and travels through Earth’s atmosphere. It excites traces of sodium 90 kilometers (50 miles) up in Earth’s upper atmosphere so that the system can measure the atmospheric turbulence. The telescope’s individual instruments then use a system of deformable mirrors to compensate for the effect of the turbulence and achieve sharp images of stars, planets, and galaxies at resolutions that rival space-based instruments. The dim lights inside the dome, turned on during telescope operation, cast the dome interior in a red glow. Through the dome opening, you can see stars streaking across the sky — the result of the long exposure used to capture this photo. You can see another view of the interior in another image from the same night here.