English: This image shows Gemini North, one half of the International Gemini Observatory, operated by NSF’s NOIRLab, using a yellow-colored laser beam to adjust its adaptive optics system during the commissioning of its new TOPTICA laser in 2018. This laser emanates from just above the telescope and travels through Earth’s atmosphere to a layer roughly 90 kilometers (50 miles) up. There, it excites traces of sodium gas to produce a glowing ‘artificial star’ which is then used to sample the atmospheric turbulence at lower altitudes. This measurement allows the adaptive optics system to move deformable mirrors on the telescope to compensate for the turbulence. This system allows Gemini North to achieve images of stars, planets, and galaxies at resolutions that rival space-based telescopes. The laser may seem bright, but this is due to the long exposure of the picture — you can see the stars trailing across the night sky through the open dome indicating the long exposure time. The TOPTICA laser of the observatory is generally dim to the naked eye, depending on how close you are standing to it. You can see another view of the commissioning here.