When you can work with a deformable mirror that compensates for atmospheric distortions, wondrous things can emerge. The Gemini Observatory (Mauna Kea, HI) used such a system coupled with a laser guide star as reference to produce an image of fast-moving ‘bullets’ of gas and the wakes they leave as they move through molecular hydrogen in the Orion Nebula. Some 1500 light years away from Earth, this stellar nursery has much to teach us about the birthing of stars.
What we’re looking at appears to be the movement of clumps of gas that have been ejected from within the nebula by some kind of violent event. They’re moving outward at about 400 kilometers per second, vast gaseous agglomerations roughly ten times the size of Pluto’s orbit around the Sun. At the tip of each clump you can see the blue glow of iron atoms shock-heated by friction with the surrounding cloud. The long wakes of their motion appear as orange smudges in the image below.
Image: This composite image at infrared wavelengths was obtained using the Gemini North laser guide star system in conjunction with the ALTAIR adaptive optics system and the NIRI near-infrared imager. The image shows the Orion “bullets” as blue features and represents the light emitted by hot iron (Fe) gas. The light from the wakes, shown in orange, is from excited hydrogen gas. The images were taken at f/14 through the Fe II, H2 1-0 and K-band filters and then combined into one color composite image. The field of view of this image is about 50 arcseconds across and structure on 0.1 arcsecond (2 pixel) scales is visible. Credit: Gemini Observatory.
These are young features, their age estimated at less than a thousand years since ejection. The beauty of this work is that the imagery is precise enough for astronomers to follow developments as the bullets of gas push ever outward through the Nebula. Says Michael Burton (University of New South Wales):
“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…[S]mall changes in the structures are expected from year to year as the bullets continue their outward motion.”
Burton’s fascination is well founded, as he and David Allen (Anglo-Australian Observatory) were the first to explain the origin of the Orion bullets some 15 years ago. But beyond the bullets themselves, the exciting news is the progress being made in adaptive optics. Gemini’s system settles down the atmospheric jitter that makes stars seem to twinkle. The laser guide star it creates is an artificial reference point that allows it to measure how the atmosphere is distorting near-infrared starlight and correct for it. As we perfect these technologies, long observing runs that might otherwise prove impractical for space-born telescopes will become available to astronomers here on Earth.