RB199 contains filamentary structures of hot gas known as "ram pressure fireballs". These fireballs are actively forming stars. After forming, the stars are no longer subjected to a ram pressure force, causing them to be left behind in a tail as the gas structure is accelerated.
^Yoshida, Michitoshi; Yagi, Masafumi; Komiyama, Yutaka; Furusawa, Hisanori; Kashikawa, Nobunari; Koyama, Yusei; Yamanoi, Hitomi; Hattori, Takashi; Okamura, Sadanori (2008). "Strange Filamentary Structures ("Fireballs") around a Merger Galaxy in the Coma Cluster of Galaxies". The Astrophysical Journal. 688 (2): 918–930. arXiv:0807.2573. Bibcode:2008ApJ...688..918Y. doi:10.1086/592430. S2CID118445050.