S2 stream. Shreds of a primitive dwarf galaxy

The S2 stream is a kinematically cold stream that is plunging downwards through the Galactic disc. It may be part of a hotter and more diffuse structure called the Helmi stream....S2星流（S2 stream）是一条运动学冷星流，正俯冲穿过银盘。它可能是一个被称为赫尔米星流（Helmi stream）的更炽热且弥散度更高的结构的一部分。