New ‘Jellyfish Galaxy’ Discovered With Star-Birthing ‘Tentacles’ Trailing Behind It
A team of astrophysicists has peered 8.5 billion years into the past and found something unexpected drifting through an ancient galaxy cluster: a galaxy that looks like a jellyfish trailing luminous tentacles through space.
The discovery, made with the James Webb Space Telescope, is the most distant jellyfish galaxy ever observed — and it’s raising new questions about how quickly the universe’s most violent forces got to work reshaping galaxies.
The galaxy, named COSMOS2020-635829, was identified by researchers at the University of Waterloo.
Their findings are published in The Astrophysical Journal.
What Gives a Jellyfish Galaxy Its Tentacles?
A jellyfish galaxy is found in dense galaxy clusters and appears to be “dripping” gas, forming long, tentacle-like tails of newborn stars trailing behind it.
The visual resemblance to a jellyfish gliding through deep water is striking — except this creature spans tens of thousands of light-years.
The process behind those tails is violent. It’s called ram-pressure stripping: the hot, dense intergalactic medium inside a cluster pushes against a galaxy as it moves through, tearing away its interstellar gas.
Think of a cosmic headwind — the surrounding material acts like a powerful gale, ripping gas from the galaxy and sculpting it into dramatic trailing structures.
What’s happening inside those tails caught the team’s attention.
COSMOS2020-635829 has a normal disc structure with bright blue knots within its gas trails. Those blue knots are very young stars, and their presence suggests stars are forming outside the main galaxy within the stripped gas.
New stars being born in the galaxy’s wake — life from destruction.
More About the James Webb Space Telescope
The James Webb Space Telescope (JWST) made this observation possible.Built by NASA, ESA, and CSA, it is the largest, most powerful infrared space observatory ever launched.
Webb went up on December 25, 2021, and now orbits the sun one million miles from Earth, using a 6.5-meter gold-coated mirror to peer through cosmic dust and observe the very first galaxies formed after the Big Bang.
Webb’s infrared capabilities let it see things that were invisible before, including galaxies so ancient and distant that their light has been stretched into infrared wavelengths by the expansion of the universe.
That power is exactly what allowed the Waterloo team to spot COSMOS2020-635829.
The galaxy was identified in the COSMOS field (Cosmic Evolution Survey Deep field), a region frequently studied because it sits far from the Milky Way’s plane.
Minimal interference from stars and dust, a clear view of distant galaxies, and visibility from both hemispheres make it one of the cleanest windows astronomers have into the deep universe.
“We were looking through a large amount of data from this well-studied region in the sky with the hopes of spotting jellyfish galaxies that haven’t been studied before,” Dr. Ian Roberts, Banting Postdoctoral Fellow at the Waterloo Centre for Astrophysics in the Faculty of Science, said in a news release.
“Early on in our search of the JWST data, we spotted a distant, undocumented jellyfish galaxy that sparked immediate interest,” he added.
What Makes This Discovery So Unique?
COSMOS2020-635829 has a redshift of z = 1.156. Astronomers are seeing it as it existed about 8.5 billion years ago. When the light from this jellyfish galaxy first began its journey toward us, our own sun and solar system did not yet exist. Earth wouldn’t form for roughly another 3.9 billion years.
That extreme distance is what makes the find so unusual. Jellyfish galaxies have been documented before, but never this far back in cosmic time.
The jellyfish galaxy identification alone would be noteworthy. But the team made three additional discoveries that push the timeline of cosmic evolution further back than scientists previously expected.
“The first is that cluster environments were already harsh enough to strip galaxies, and the second is that galaxy clusters may strongly alter galaxy properties earlier than expected,” Roberts said, per the release.
The violent forces that shape and sometimes destroy galaxies were already at work in the universe’s relative youth — billions of years earlier than many models had suggested.
“Another is that all the challenges listed might have played a part in building the large population of dead galaxies we see in galaxy clusters today. This data provides us with rare insight into how galaxies were transformed in the early universe,” he added.
“Dead galaxies” — galaxies that have stopped forming new stars — fill galaxy clusters today. One of the enduring puzzles of modern astrophysics is explaining how they got that way.
COSMOS2020-635829 suggests that the process of killing galaxies, of stripping away the gas they need to birth new stars, may have been underway far earlier in cosmic history than previously understood.
What Comes Next
Each discovery from the James Webb Space Telescope reshapes our picture of how the universe evolved — how galaxies were born, how they changed, and how some of them died.
COSMOS2020-635829, that distant jellyfish trailing its luminous tentacles through a galaxy cluster 8.5 billion years in the past, shows that the universe still holds surprises in its oldest light.
Webb, a publicly funded instrument built through international partnership, is only beginning to reveal them.
Production of this article included the use of AI. It was reviewed and edited by a team of content specialists.
