Astrophysicists Discover 'Jellyfish' Galaxy Using James Webb Telescope

Astronomers from Canada and Switzerland have recently identified a new galaxy designated as COSMOS2020-635829, utilizing the advanced capabilities of the James Webb Space Telescope (JWST). This significant discovery, detailed in a research paper published on June 17, 2025, highlights the galaxy's unique characteristics that classify it as a 'jellyfish' galaxy, primarily due to its undergoing process of ram pressure stripping, a phenomenon that affects gas within galaxies.

The term 'jellyfish galaxy' refers to galaxies that exhibit long, trailing streams of gas and young stars, resembling the morphology of jellyfish. These galaxies are typically found within clusters and experience gas stripping as they traverse through the intracluster medium, which often leads to bursts of star formation in the released gas. Ian D. Roberts, an astrophysicist at the University of Waterloo in Canada, led the research team, which utilized high-resolution imaging from the JWST to uncover a symmetric stellar disk paired with a singular tail of star-forming knots, making COSMOS2020-635829 a noteworthy example of this type of galaxy.

In their study, the researchers observed that COSMOS2020-635829 is associated with a cluster-mass, X-ray detected overdensity and features a one-sided collection of blue, star-forming extra-planar knots that coincide with an ionized gas tail. The star-forming knots in the galaxy's tail possess stellar masses on the order of 100 million solar masses and exhibit star-formation rates between 0.1 and 1 solar mass per year, accounting for approximately one percent of the total stellar mass of COSMOS2020-635829.

The galaxy has an estimated redshift of approximately 1.156 and a stellar mass near 10 billion solar masses, with a notable star-formation rate of around 100 solar masses per year. Moreover, its X-ray luminosity has been recorded at about 8 tredecillion erg/s, marking it as a compelling candidate for jellyfish galaxy classification at a redshift exceeding 1.0.

This finding not only adds to the catalog of known jellyfish galaxies but also provides critical insights into the mechanisms that regulate star formation and galaxy evolution in the high-redshift universe. The authors of the paper emphasize that their study reinforces the understanding that ram pressure stripping can significantly affect group and cluster galaxies at redshifts greater than 1, contributing to environmental quenching during what is referred to as 'Cosmic Noon,' a term used to describe a period when star formation peaked across the universe.

The implications of this discovery extend beyond mere classification; it enhances our understanding of the conditions that govern galaxy formation and evolution. The unique features of COSMOS2020-635829 underscore the importance of further observational studies using the JWST and other advanced telescopes, which could yield additional revelations about the universe's evolution and the fundamental processes driving the lifecycle of galaxies. Such insights may inform future astrophysical models and add depth to our comprehension of cosmic phenomena.

This groundbreaking work highlights the capacity of the JWST to explore the distant universe, shedding light on the intricate dynamics of galaxy clusters and their interactions with the intergalactic medium. As further data emerges, the scientific community anticipates that revelations about jellyfish galaxies and their role in the broader context of cosmic evolution will continue to unfold.