LDN 1551 is a 50 solar mass dark molecular cloud in the constellation of Taurus. Located 450 light years from earth, LDN 1551 is remarkable for a large number of young protostars and more evolved young stellar objects (YSO’s) for such a small region. Many of these protostars are very active and emit powerful energetic outflows often in opposite directions. The complex cloud in the upper right of the image (in the lower right in the chart below) shows a number of bipolar molecular outflows and Herbid Haro objects which represent the visible light signatures of these evolving infant stars. Towards the center in the chart below (rotated 90 degrees clockwise from the image) is the archetypical protostar system L1551 IRS5. Protostars are areas within molecular clouds where stars are forming. The process begins when areas of increased density within a molecular cloud begin to condense and contract, increasingly driven by its own gravity. The early protstars are surrounded by dusty envelopes of gas hundreds of AU across As these objects gain mass their gravity increases, causing more material to spiral inwards. This causes the disk of surrounding material to rotate faster and faster. Eventually the inner part of the disk rotates too fast for the outermost parts to keep up, causing this to be lost. The remaining, fast spinning inner disk is called a Keplerian Disk. Most of the material in this will spiral in and add to the mass of the developing star, though some may remain in orbit forming a planetary system.
Chart of the region (Rotated 90 degrees clockwise from the image) courtesy DAVID DEVINE, BO REIPURTH AND JOHN BALLY, "L1551 NE OR L1551 IRS 5: WHICH SOURCE DRIVES HH 28/29?" THE ASTRONOMICAL JOURNAL, 118:972È982, 1999 August.
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