Galaxy drags trail of stars behind it
Collisions with hot gas trigger streaks of stellar births

STAR RIVERS The galaxy ESO 137-001, 200 million light-years away, leaves trails (shown in blue in this false-color Hubble Space Telescope image) of gas and newly born stars as it plows through the Norma Cluster. Bright stars in the foreground sit within our galaxy.
Ming Sun/UAH, Serge Meunier, NASA, ESA