Binary formation is an important aspect of star formation. One possible route for close-in binary formation is disk fragmentation^1,2,3. Recent observations show that small-scale asymmetries (<300 au) around young protostars^2,4, although not always resolving the circumbinary disk, are linked to disk phenomena^5,6. In later stages, resolved circumbinary disk observations⁷ (<200 au) show similar asymmetries, suggesting that the asymmetries arise from binary–disk interactions^8,9,10. We observed one of the youngest systems to study the connection between disk and dense core. We find a bright and clear streamer in chemically fresh material (carbon-chain molecular species) that originates from outside the dense core (>10,500 au). This material connects the outer dense core with the region where asymmetries arise near disk scales. This new structure type, ten times larger than those seen near disk scales, suggests a different interpretation of previous observations: large-scale accretion flows funnel material down to disk scales. These results reveal the under-appreciated importance of the local environment on the formation and evolution of disks in early systems^11,12 and a possible initial condition for the formation of annular features in young disks^13,14.

双星形成是恒星形成的重要方面。近距离二进制形成的一种可能途径是磁盘碎片^1,2,3。最近的观察表明，年轻的原恒星^2,4周围的小尺度不对称性（<300 au），尽管并不总是能解决环盘，但与盘现象^5,6有关。在以后的阶段，已解析的周向盘观测结果⁷（<200 au）表现出相似的不对称性，这表明不对称性是由二进制-磁盘间的相互作用引起的^8,9,10。我们观察到了最年轻的系统之一，用于研究磁盘和密集内核之间的连接。我们发现化学上新鲜的原料（碳链分子种类）中有明亮而清晰的流光，该材料来自密实核（> 10,500 au）的外部。这种材料将外部致密芯与在磁盘刻度附近出现不对称的区域连接起来。这种新的结构类型比圆盘刻度尺附近的尺寸大十倍，对以前的观察结果提出了不同的解释：大规模的吸积使漏斗材料向下流向圆盘刻度尺。这些结果揭示了早期系统^11,12中磁盘形成和演化过程中局部环境的重要性不足，以及年轻磁盘^13,14中环形特征形成的可能初始条件。