A high-flying observatory is about to be grounded. SOFIA — the Stratospheric Observatory For Infrared Astronomy — has been operating for a decade. But its work no longer matches NASA’s science goals, so it’ll be shut down by the end of the month. SOFIA consists of a Boeing 747 with a door in its side. At high altitude, the door opens to reveal a large infrared telescope. Water vapor in Earth’s lower atmosphere absorbs infrared light. At an altitude of seven or eight miles, though, the telescope is above 99 percent of the water vapor, providing a clear view of the infrared sky. And the observatory can travel around the world to view interesting targets. Infrared wavelengths are especially useful for studying fairly cool objects: planets and comets, clouds of interstellar gas and dust, and the cocoons around young stars. SOFIA studied all of those objects and more. The project has had a troubled history, though. It ran years behind schedule and tens of millions of dollars over budget. NA
