Substantial reservoirs of molecular hydrogen in the debris disks around young stars
Substantial reservoirs of molecular hydrogen in the debris disks around young stars
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年轻恒星周围的碎片盘中蕴藏着大量的分子氢
作者：
W. Thi;G. Blake;E. Dishoeck;G. V. Zadelhoff;J. Horn;E. Becklin;V. Mannings;A. Sargent;M. V. D. Ancker;A. Natta
星周吸积盘将物质从分子云转移到年轻的恒星和行星形成的地点。在前主序星周围观察到的圆盘具有与4.5 Gyr前形成我们太阳系的前太阳星云相一致的特性。但是，根据对示踪分子一氧化碳的观测，围绕着附近15%以上主序星的“碎片”盘似乎含有非常少量的气体：这些观测得出的气体/尘埃比远小于0.1，而星际值约为100。在这里，我们报告了分子氢（H2）的最低旋转跃迁的观测结果，这些观测结果揭示了Pictureso β，Ceti 49和HD 135344周围的碎片盘中存在大量气体。根据这些数据计算出的气体质量比CO观测值大几百到一千倍，产生的气体/尘埃比与星际值相同。
Circumstellar accretion disks transfer matter from molecular clouds to young stars and to the sites of planet formation. The disks observed around pre-main-sequence stars have properties consistent with those expected for the pre-solar nebula from which our own Solar System formed 4.5 Gyr ago. But the ‘debris’ disks that encircle more than 15% of nearby main-sequence stars,,,appear to have very small amounts of gas, based on observations of the tracer molecule carbon monoxide,,: these observations have yielded gas/dust ratios much less than 0.1, whereas the interstellar value is about 100 (ref. ). Here we report observations of the lowest rotational transitions of molecular hydrogen (H2) that reveal large quantities of gas in the debris disks around the stars β Pictoris, 49 Ceti and HD135344. The gas masses calculated from the data are several hundreds to a thousand times greater than those estimated from the CO observations, and yield gas/dust ratios of the same order as the interstellar value.