Astronomers have discovered a new “jellyfish” galaxy about 12 billion light-years away using the James Webb Space Telescope. It appears to have tentacle-like streams of gas and stars trailing off one side, a signature feature of jellyfish galaxies. These galaxies develop such trails via ram pressure stripping as they move through dense cluster environments, triggering star formation in the stripped gas. The find was made by Ian Roberts of Waterloo University, and details are described in a preprint on arXiv. More analysis is needed to confirm the classification, but early signs strongly suggest this object is indeed a jellyfish galaxy.
What Are Jellyfish Galaxies?
According to NASA, jellyfish galaxies are so named because of the long, trailing streams of gas and young stars that extend from one side of the galaxy. This phenomenon occurs when a galaxy moves rapidly through the hot, dense gas in a cluster, and ram pressure strips material away. The stripped gas forms a wake behind the galaxy, and this wake often lights up with bursts of new star formation. At the same time, the process can deprive the galaxy’s core of gas, potentially slowing star formation in the galaxy’s center.
Because the jellyfish stage is short-lived on cosmic timescales, astronomers rarely catch galaxies in this act. Studying jellyfish galaxies gives scientists insight into how dense environments affect galaxy evolution and star formation.
Discovery and Future Research
The researchers caution that the galaxy’s apparent “tentacles” may partly be an artifact of the imaging method. If confirmed, this object (COSMOS2020-635829) would be the most distant known jellyfish galaxy, offering a rare glimpse of how ram pressure stripping and cluster-driven quenching operated in the early cosmos. As the study authors note, finding a jellyfish at z>1 reinforces the idea that these environmental effects were already at work near the peak of cosmic star formation.
