charles

NGC 1999: South of Orion



影像版權與提供: Robert Gendler

Explanation:
      South of the large star-forming region known as the Orion Nebula, lies bright blue reflection nebula NGC 1999. The nebula is marked with a dark inverted T-shape at the lower left in a broad cosmic vista that spans over 10 light-years. The dark shape is a dense gas and dust cloud, or Bok globule, seen in silhouette against the bright nebula, and likely a site of future star formation. At the edge of the Orion molecular cloud complex some 1,500 light-years distant, NGC 1999's illumination is provided by the embedded variable star V380 Orionis. The region abounds with energetic young stars producing jets and outflows that create luminous shock waves, including HH (Herbig-Haro) 1 and 2 just below and left of NGC 1999, and the apparent cascade of reddish arcs and bow shocks beginning at the upper right. The stellar jets and outflows push through the surrounding material at speeds of hundreds of kilometers per second.

說明:
      在大型恆星形成獵戶座大星雲的南邊，有個稱為NGC 1999的藍色反射星雲。在上面這幅跨度超過十光年的寬廣星野裡，影像左下方的倒T型天體就是這個星雲。這個暗色的天體是個緻密的雲氣和塵埃雲，或稱為包克雲球，在光亮雲氣的襯托下才顯現它的剪影，而它很可能會是未來恆星形成的所在。NGC 1999位在離我們約有一千五百光年的獵戶座分子雲團之邊緣，受到它內部的變星獵戶座V380星之照亮。這個區域內到處都是活耀的年輕恆星，它們所發出的噴流和物質流造成明亮的震波，包括NGC 1999左下方的HH1(Herbig-Haro)與HH2天體，與及它右上方一連串紅色的弓形震波弧。年輕恆星所發出的噴流和物質流，以每秒數百公里的高速衝撞周圍的雲氣物質。

資料來源: Scientific American
               Department of Physics, NCKU