Using a guide-star laser to find bullets

The Gemini Observatory has been using laser generated guide stars as part of their adaptive optics program for a while but they've recently release some stunning images of the Orion nebula featuring supersonic "bullets" of gas and their associates wakes through the nebula.

"What I find stunning about the new image is the detail it shows, which was blurred out in any previous studies, revealing the structure of the bullets and their trailing wakes as they run into the surrounding molecular cloud," said Michael Burton of the University of New South Wales who, along with the late David Allen (Anglo-Australian Observatory) were the first to suggest the origin of these spectacular bullets 15 years ago. "This level of precision will allow the evolution of the system to be followed over the next few years, for small changes in the structures are expected from year to year as the bullets continue their outward motion."

The exceptional resolution of the new image was made possible by adaptive optics technology in place at Gemini Observatory. With a laser guide star as a reference and a rapidly deformable mirror for real-time correction, astronomers can compensate for most of the atmospheric distortions that blur the near-infrared image of a star whose light reaches the telescope's primary mirror. The system deploys a yellow/orange solid-state sodium laser that produces the artificial guide star by exciting and causing a small column of sodium gas about 90 kilometers (56 miles) up in our atmosphere to glow. The artificial star it creates becomes a reference star for the adaptive optics system, and allows it to determine how the atmosphere distorts the incoming near-infrared starlight.