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While monitoring stars in the young cluster NGC 2264, Kearns & Herbst found a star with a unique and bizarre light curve. The object, which has come to be known as KH 15D, undergoes periodic eclipses that are remarkable for their depth (3.5 mag) and duration (currently over 50% of the 48-day period). It was suspected from the beginning that the eclipses are caused by circumstellar material, but it took a long time to confirm that hypothesis and clarify the geometry of the system. I will explain how this was done, using a combination of optical photometry, spectroscopy, polarimetry, and an analysis of archival photographs. The occulting material can be used as a "natural coronagraph" to map out the environment of this young (and possibly planet-forming) star. |