近日，加拿大维多利亚大学的Jessica Speedie&Ruobing Dong及其研究团队取得一项新进展。经过不懈努力，他们揭示行星形成盘中的引力不稳定性。相关研究成果已于2024年9月4日在国际权威学术期刊《自然》上发表。

在此，该研究团队利用阿塔卡马大型毫米波/亚毫米波阵列（ALMA）对AB Aurigae周围星盘的¹³CO和C¹⁸O谱线发射进行了深度观测，并据此提出了该星盘中存在引力不稳定性的动力学证据。观测到的动力学信号与模拟和解析模型的预测高度相似。通过定量比较，研究人员推断出，在距离天体1″至5″的范围内，星盘的质量可高达恒星质量的三分之一。

据悉，恒星周围行星形成的经典理论认为，行星是由最初小得多的种子逐渐增长而来的。长期以来，另一种备受考虑的理论提出，如果星盘在引力上是不稳定的，那么巨大的原行星可以直接由引力不稳定性引发的巨大螺旋臂坍缩片段形成。

要使这种情况成为可能，星盘的质量必须相对于中心恒星足够大：通常认为，星盘与恒星的质量比为1:10是触发引力不稳定性的大致阈值，这会引发显著的非开普勒动力学效应，并产生明显的螺旋臂。尽管历史上估计星盘质量一直具有挑战性，但气体的运动可以通过其对星盘速度结构的影响来揭示引力不稳定性的存在。

附：英文原文

Title: Gravitational instability in a planet-forming disk

Author: Speedie, Jessica, Dong, Ruobing, Hall, Cassandra, Longarini, Cristiano, Veronesi, Benedetta, Paneque-Carreo, Teresa, Lodato, Giuseppe, Tang, Ya-Wen, Teague, Richard, Hashimoto, Jun

Issue&Volume: 2024-09-04

Abstract: The canonical theory for planet formation in circumstellar disks proposes that planets are grown from initially much smaller seeds. The long-considered alternative theory proposes that giant protoplanets can be formed directly from collapsing fragments of vast spiral arms induced by gravitational instability—if the disk is gravitationally unstable. For this to be possible, the disk must be massive compared with the central star: a disk-to-star mass ratio of 1:10 is widely held as the rough threshold for triggering gravitational instability, inciting substantial non-Keplerian dynamics and generating prominent spiral arms. Although estimating disk masses has historically been challenging, the motion of the gas can reveal the presence of gravitational instability through its effect on the disk-velocity structure. Here we present kinematic evidence of gravitational instability in the disk around AB Aurigae, using deep observations of ¹³CO and C¹⁸O line emission with the Atacama Large Millimeter/submillimeter Array (ALMA). The observed kinematic signals strongly resemble predictions from simulations and analytic modelling. From quantitative comparisons, we infer a disk mass of up to a third of the stellar mass enclosed within 1″ to 5″ on the sky.

DOI: 10.1038/s41586-024-07877-0

Source: https://www.nature.com/articles/s41586-024-07877-0