The origin of stars and their planetary systems

我们有幸生活在人类历史上的一个独特时刻。 关于是否存在像我们这样的其他世界以及它们是否支持生命的古老问题已经被直接科学调查所揭示。 在过去的5年里，赫歇尔空间天文台已经揭示了恒星在哪里以及如何诞生。 阿塔卡马毫米阵列（阿尔马）刚刚开始绘制伴随着所有恒星诞生的行星诞生的气体盘。 开普勒太空天文台确定了数千个新的行星候选者，并发现了大量的行星和超级地球。 我们比以往任何时候都更有信心解决恒星及其相关行星系统如何形成和演化的问题。 ** 在本研究计划中，我们将开发新的计算和理论途径，在三个层面上解决这些基本且相互关联的问题：恒星如何在主导星星形成云的高度丝状结构中形成？ 行星是如何形成、迁移并在伴随恒星诞生的气体盘中获得其独特的化学成分的？ 最后，岩石类地球世界是如何配备了水和生物分子，如氨基酸，这是我们所知道的生命发展的基础？ ** 恒星形成于稠密、寒冷、磁化和湍流的气体中，聚集成离散的分子云。 恒星的质量从太阳质量的百分之几到几百倍不等，它们的质量分布似乎是普遍的。 赫歇尔揭示，分子云被组织成大量致密的细丝，从数十秒差距（一秒差距是距离我们最近的星星的典型长度）延伸到亚秒差距尺度。 此外，恒星形成于细丝内的那些区域，在这些区域中，单位长度的质量超过一个临界值，超过这个临界值，引力就会接管，导致坍缩。 在这个提议中，我们将使用新的3D计算机代码和先进的理论方法来追踪这些细丝内的气体运动和磁场，并计算年轻恒星产生的辐射对气体的反馈效应，以确定这些过程如何产生强大而普遍的恒星质量分布。 ** 行星形成于围绕年轻恒星运行的原子和分子气体和尘埃盘中。 气体盘存在了300万到1000万年，然后才被年轻恒星的辐射驱散。 在这段时间里，年轻的形成行星与气体发生强烈的引力相互作用，导致它们迅速迁移。 我们已经开发了一个理论模型，其中在磁盘的功能，如密度跳跃或气体温度的突然变化作为动态行星陷阱。 在这里，行星在数百万年的时间里缓慢地向内移动（正如观察到的那样），并吸积了大部分的铁，岩石，冰和气体。 我们现在可以预测行星的组成，通过将行星在陷阱中运动的图像与这些圆盘的化学和组成图像联系起来。 这项工作将为行星和大气结构的建模者提供急需的有关行星组成的信息。 ** 最后，我们所知道的生命的发展需要生物分子，如氨基酸，它们是蛋白质的组成部分。 某些类别的陨石富含氨基酸，可能在为地球生命做准备方面发挥了关键作用。 在这个计划中，我们将结合联合收割机模型的磁盘形成和化学与合成的氨基酸在陨石母体预测的生物分子的种类，预计将淋浴到年轻的形成行星。 这使我们能够解决生命的条件在其他行星系统中的普遍性。

We are privileged to be living at a unique moment in human history. The age old questions of whether there are other worlds such as our own and whether they support life have been opened up to direct scientific investigation. Over the last 5 years, the Herschel space observatory has revealed where and possibly how stars are born. The Atacama Millimetre Array (ALMA) has just started to map the gaseous disks in which planets are born that accompany the birth of all stars. The Kepler space observatory identified thousands of new planetary candidates and revealed extensive populations of Jupters, as well as SuperEarths. We are poised as never before to address the question of how stars and their associated planetary systems form and evolve. **In this research program we will develop new computational and theoretical avenues to address these fundamental and interrelated questions on three levels: how do stars form in the highly filamentary structures that dominate star forming clouds? How do planets form, migrate, and acquire their unique chemical compositions in the gasous disks that accompany stellar birth? And finally, how are the rocky Earth-like worlds equipped with the water and biomolecules such as amino acids that are fundamental to the development of life as we know it? **Stars form in dense, cold, magnetized and turbulent gas gathered into discrete molecular clouds. Stellar masses range from a few hundredths a hundred times the mass of our Sun, and their mass distribution seems to be universal. Herschel revealed that molecular clouds are organized into a plethora of dense filaments extending from tens of parsecs (a parsec is typical length to our nearest star) down to sub parsec scales. Moreover, stars form in those regions within filaments where the mass per unit length exceeds a critical value above which gravitational forces take over leading to collapse. In this proposal, we will use new 3D computer codes and advanced theoretical methods to trace the gas motions and magnetic fields within these filaments, as well as compute the effect of feedback on the gas by radiation produced by the young stars, to determine how these processes yield a robust and universal stellar mass distribution. **Planets form within disks of atomic and molecular gas and dust that orbit young stars. The gas disks live for 3-10 million years before they are finally dispersed by the radiation from young stars. During this time, young forming planets undergo strong gravitational interactions with the gas, leading to their rapid migration. We have developed a theoretical model wherein features in the disk such as density jumps or sudden changes in gas temperature act as dynamical planet traps. Here, planets move slowly inwards over millions of years (as observed) and accrete most of their composite iron, rock, ice, and gas. We will now be able to predict the composition of planets by connecting this picture of planets moving in their traps with a picture of the chemistry and composition of these disks. This work will provide modelers of planetary and atmospheric structure with critically needed information about the composition of planets. **Finally, the development of life as we know it requires biomolecules such as amino acids that are the building blocks of proteins. Certain classes of meteorites are rich in amino acids and may have played a critical role in preparing our Earth for life. In this program, we will combine models for disk formation and chemistry with the synthesis of amino acids in meteorite parent bodies to predict the kinds of biomolecules that would be expected to shower onto young forming planets. This allows us to address how universal the conditions for life are in other planetary systems.