An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

Any of various marine coelenterates of a soft, gelatinous structure, especially one with an umbrella like body and long, trailing tentacles; medusa (dictionary.com).

→ jelly; → fish.

Medusâ, from Gk. Medousa, literally "guardian," from medein "to protect, rule over."

A type of galaxy exhibiting "tentacles" (tails) of material that appear to be stripped from the main body of the galaxy, making it resemble a jellyfish. Such type of galaxies occur in → galaxy clusters and are produced by a process called → ram pressure stripping. The mutual → gravitational attraction between galaxies causes them to fall at high speed into the clusters, where they encounter a hot → intracluster medium (ICM) with dense gas. The falling galaxy feels a powerful wind, forcing tails of gas out of the galaxy's disk and triggering → starbursts within it. Jellyfish galaxies have mainly been observed in nearby clusters (e.g., Virgo, Coma, A1367, A3627, Shapley). A few examples have been identified in clusters at → redshifts z ~ 0.2-0.4, and there is accumulating evidence for a correlation between the efficiency of the stripping phenomenon and the presence of shocks and strong gradients in the X-ray → intergalactic medium (Poggianti et al., 2016, AJ 151, 78).

→ jellyfish; → galaxy.