OBSERVATIONAL RESEARCH OF ACCRETION IN PROTOPLANETARY DISKS

在这项研究中，我们通过天文观测研究了恒星形成和原行星盘形成的动力坍缩。在1996财政年度的研究中，在两颗新的原恒星周围发现了动力下降的直接证据。这两个天体都在大约1000AU（天文单位）的包络半径处显示出旋转和下落，这表明在中心天体周围存在100 AU尺度的原行星盘，这实际上已经从其他观测中得到了证实。因此，我们的结果为原行星盘的形成提供了确凿的证据，原行星盘是行星系统形成的场所，是通过原恒星包层的动态吸积形成的。然后，我们根据新的观测，在1997财政年度研究了原恒星包层的统计特征，发现虽然包层中气体的特定角动量与半径大于0.03秒差距（pc）时半径的1.6次方成正比，但它与半径无关，并且在半径小于0.03秒差距时，它约为10^<-3> km ^<-1>pc。这可能意味着原恒星包层的动态坍缩发生在半径0.03个单位的范围内，因此，气体保持其特定的角动量，形成半径相当于100个天文单位的原行星盘。这个新的结果很自然地解释了太阳系和原行星盘的100天文单位大小。

In this research we investigated, through astronomical observations, dynamical collapse in star formation and formation of protoplanetary disks.Direct evidence of dynamical infall was found around two new protostars during the research in the fiscal year 1996. Both objects showed rotation as well as infall at the envelope radius of about 1000AU (=Astronomical Unit), suggesting the presence of 100 AU scale protoplanetary disks around the central objects, which were actually confirmed from other observations. Our results hence gave firm evidence of protoplanetary disks, which would be the site of planetary system formation, to be formed through dynamical accretion in protostellar envelopes.We then studied statistical characteristics of protostellar envelopes in the fiscal year 1997 based upon new observations, finding that, while the specific angular momentum of gas in envelopes is proportional to the 1.6-th power of the radius at radii larger than 0.03 parsec (pc), it is independent of radius and is constant at about 10^<-3> km s^<-1>pc at radii less than 0.03pc. This may mean that dynamical collapse in protostellar envelopes occurs inside radii of 0.03 pc and that, as a result, the gas keeps its specific angular momentum to form protoplanetary disks with their radii comparable to 100 AU.This new result naturally explains the 100 AU size scale of the solar system as well as that of protoplanetary disks.