Jellyfish galaxy JW39, more than 900 million light-years away in the constellation eat berenices, It hangs peacefully in this image from the NASA/ESA Hubble Space Telescope.
Despite its appearance, this galaxy is wandering in a fiercely hostile environment: cluster of galaxies, Compared to their more isolated counterparts, galaxies in galaxy clusters are often distorted by the gravitational pull of their larger neighbors, which can bend galaxies into a wide variety of shapes.
If that weren’t enough, the space between galaxies in a cluster is also occupied by an extremely hot plasma known as the intracluster medium. Although this plasma is extremely tenuous, galaxies moving through it feel almost like swimmers fighting the current, and this interaction can strip galaxies of their star-forming gas.
This interaction between the intracluster medium and the galaxies is called ram shading and is the process responsible for the trailing plumes of the Jellyfish Galaxy. As JW39 moved through the cluster, pressure from the intracluster medium dislodged gas and dust into long ribbons of star formation that now protrude from the galaxy’s disk, NASA reports.
Astronomers using Hubble’s Wide Field Camera 3 studied these trailing plumes in detail, as they are particularly extreme environments for star formation. Surprisingly, they found that star formation in the “tentacles” of jellyfish galaxies was not particularly different from star formation in the Milky Way’s disk.