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Horsehead Nebula
Robert Vanderbei
Department of Operations Research and Financial Engineering
Modern digital cameras are creating a revolution in astroimaging. When well-cooled, these devices become almost perfect photon counters. Combine them with narrow band dichroic filters and computer-based image processing tools and it is now possible to take images of interesting astronomical objects from light-polluted New Jersey skies with modest equipment, and these images rival the best images taken by the largest telescopes only, say, twenty years ago. This image, for example, was taken with a 4Ē refractor telescope from a location just 5 miles north of Princeton. The dark area in the lower part of the picture is an interstellar dust cloud. A multitude a stars are hidden behind this cloud leaving only a small number of foreground stars for us to see. The interesting part of the cloud is, of course, its edge, which crosses the middle of the image. Above the edge, we see light that was first emitted by stars we canít see, then absorbed by interstellar hydrogen atoms, and finally re-emitted at the so-called hydrogen-alpha wavelength. The interesting protrusion of the dark cloud is called the Horsehead nebula.