Typically protoplanetary disks and the stars that they encircle are modelled as isolated systems. However, extended gaseous structures (for instance, streamers) have been observed around such disks, which suggests that they are fed by material from the wider surroundings, even when the disk is mature. Using a simple model, Andrew Winter and colleagues show that by incorporating continuously accreting material, observed disk masses, accretion rates, radii and lifetimes can be well reproduced. Moreover, considering a disk in the context of its star-forming region has implications even for small scales, since, for example, a relatively fast-moving star should accrete less mass from the interstellar medium (ISM), affecting the characteristics of planet formation.

Winter et al. adopt a semi-analytic model that assumes Bondi–Hoyle–Lyttleton (BHL) accretion of low-velocity ISM onto a protoplanetary disk over a period of several million years (a typical disk lifetime). The model incorporates the turbulent cascade from star-forming region to disk size scales by following density and velocity perturbations on a single volume element. Such a treatment implies that disk masses, radii and stellar accretion rates become a function of BHL accretion rate in addition to stellar mass and age. Since disks are continually replenished in this scenario, they can potentially accrete the bulk of their mass in the latter halves of their lifetimes. Accretion might also drive turbulence in the outer disk, leading to a potential spread of outer disk viscosity of several orders of magnitude.

通常，原行星盘及其围绕的恒星被建模为孤立的系统。然而，在这些圆盘周围观察到了扩展的气体结构（例如，流光），这表明即使圆盘已经成熟，它们也是由来自更广泛周围环境的物质供给的。安德鲁·温特（Andrew Winter）及其同事使用一个简单的模型表明，通过合并不断吸积的物质，可以很好地再现观察到的圆盘质量、吸积率、半径和寿命。此外，在恒星形成区域的背景下考虑圆盘，即使对于小尺度也有影响，因为，例如，相对快速移动的恒星应该从星际介质（ISM）中吸积较少的质量，从而影响行星形成的特征。

温特等人。采用半解析模型，假设 Bondi-Hoyle-Lyttleton (BHL) 在几百万年的时间内（典型的盘寿命）将低速 ISM 吸积到原行星盘上。该模型通过跟踪单个体积元素上的密度和速度扰动，整合了从恒星形成区域到盘尺寸尺度的湍流级联。这样的处理意味着除了恒星质量和年龄之外，盘质量、半径和恒星吸积率也成为 BHL 吸积率的函数。由于在这种情况下磁盘会不断得到补充，因此它们可能会在其生命周期的后半段积累大部分质量。吸积还可能驱动外盘中的湍流，导致外盘粘度可能扩散几个数量级。