Jellyfish Galaxy JW39. / EP.
More than 900 million light-years away, jellyfish galaxy JW39 floats quietly in this NASA/ESA Hubble Space Telescope image.
Contrary to its appearance, this galaxy is drifting in a very harsh environment called a galaxy cluster. Compared to more isolated galaxy clusters, galaxies within clusters are often distorted by the gravitational pull of larger neighboring galaxies, which can cause galaxies to twist into different shapes.
If that wasn’t enough, the intergalactic space within the cluster is also permeated by a very hot plasma known as the intracluster medium. Although this plasma is very tenuous, galaxies moving through it experience conditions like swimmers fighting currents, and this interaction can strip galaxies of star-forming gas.
This interaction between cluster matter and the galaxy is called sheep molting, and is the process responsible for the trailing tendrils of this jellyfish galaxy. As JW39 moved through the cluster, pressure from the cluster’s medium removed gas and dust, forming a long ribbon of star formation that now extends out of the galactic disk, NASA reports.
Astronomers used Hubble’s Wide Field Camera 3 to study these trailing vines in detail. because they are particularly extreme environments for star formation. Surprisingly, they found that star formation in the jellyfish ‘tentacles’ did not differ significantly from star formation in the galactic disk.