NASA/ESA/CSA’s James Webb Space Telescope has made groundbreaking observations of a galaxy featuring gaseous “tentacles” within a galaxy cluster at a redshift of 1.156. This remarkable finding allows us to observe the universe as it was approximately 8.5 billion years ago.

This web image highlights the jellyfish galaxy COSMOS2020-635829, with dashed circles marking four out-of-plane sources in its tail. Image credit: Roberts et al., doi: 10.3847/1538-4357/ae3824.

“The jellyfish galaxy derives its name from the long, tentacle-like streams trailing behind it,” explained Dr. Ian Roberts of the University of Waterloo and his team.

“As it travels quickly through the hot, dense galaxy cluster, the gas within the cluster acts like a powerful wind, pushing the jellyfish galaxy’s gas backward and forming a visible trail.”

“This phenomenon is referred to as ram pressure stripping.”

The research team discovered a new jellyfish galaxy through deep-space data captured by the Webb Telescope.

Named COSMOS2020-635829, this galaxy resides in the COSMOS field, a well-explored area of the sky studied extensively by various telescopes.

“While sifting through vast amounts of data from this thoroughly investigated region, we aimed to uncover previously undocumented jellyfish galaxies,” Dr. Roberts noted.

“Early in our analysis, we stumbled upon a distant, uncharted jellyfish galaxy that piqued our interest.”

COSMOS2020-635829 exhibits a typical galactic disk coupled with bright blue nodes in its trajectory, indicative of very young stars.

The ages of these stars suggest they formed in gas trails stripped from their host galaxy, a behavior characteristic of jellyfish galaxies.

Insights from this study challenge established beliefs regarding the conditions in deep space during that era.

Scientists previously thought the galaxy cluster was still in formation and that ram pressure stripping was a rare occurrence.

Dr. Roberts and his co-authors identified three further discoveries that could reshape our understanding of the cosmos.

“The first discovery indicates that the cluster environment was already intense enough to strip galaxies away. Second, the cluster can significantly alter galaxy properties sooner than anticipated,” Roberts explained.

“Finally, these dynamics might play a crucial role in forming the populations of inactive galaxies we observe in today’s galaxy clusters.”

“These findings offer pivotal insight into the evolution of galaxies in the early universe.”

For more details on this discovery, check out the paper published in the Astrophysical Journal.

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Ian D. Roberts et al. 2026. JWST reveals candidate jellyfish galaxy at z = 1.156. APJ 998, 285; doi: 10.3847/1538-4357/ae3824