JW39 Galaxy captured by Hubble appears as a jellyfish

Jellyfish galaxy JW39 hangs softly in this image from the NASA/ESA Hubble Space Telescope. Located more than 900 million light-years away in the coma constellation Berenices, this galaxy is one of several jellyfish galaxies that Hubble has been studying over the past two years.

Despite the peaceful appearance of this jellyfish galaxy, it’s lurking in a fiercely hostile environment: a galaxy cluster. Compared to their more isolated counterparts, galaxies in galaxy clusters are often distorted by the gravitational pull of larger neighbors, which can warp galaxies into a variety of shapes.

If that wasn’t enough, the space between galaxies in the cluster is also peppered with a superheated plasma known as the intracluster medium. While this plasma is very weak, galaxies moving through it experience it almost like swimmers fighting against a current, and this interaction can strip galaxies of their star-forming gas.

This interaction between the center of the inner cluster and the galaxies is called erosion ram compression and is the process responsible for the trailing tendrils of this jellyfish galaxy. As JW39 moved through the cluster, the pressure of the cluster’s medium stripped gas and dust into long, belated ribbons of star formation that now extend far out from the galactic disk.

Astronomers using Hubble’s Wide Field Camera 3 have studied these trailing tendrils in detail, because they are a particularly harsh environment for star formation. Surprisingly, they found that star formation in the “tentacles” of jellyfish galaxies was not markedly different from star formation in the galaxy’s disk.