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James Webb Reveals Glowing Bridge Linking Colliding Dwarf Galaxies Arp 269 (NGC 4490 & NGC 4485)

02:58 PM, 12/05/2025
James Webb Reveals Glowing Bridge Linking Colliding Dwarf Galaxies Arp 269 (NGC 4490 & NGC 4485)

The James Webb Space Telescope has captured a detailed infrared image of two colliding dwarf galaxies, NGC 4490 and NGC 4485 (Arp 269), about 24 million light-years away. Webb's NIRCam and MIRI resolved individual stars and the fine structure of a bright gas-and-dust bridge connecting the pair, revealing clusters of newborn stars. Analysis indicates the galaxies passed close to each other roughly 200 million years ago, with gas transfer fueling star formation as recently as 30 million years ago. This nearby system offers new insight into how low-mass, gas-rich galaxies grow and evolve — processes similar to those in the early universe.

James Webb Captures a Cosmic Tug-of-War

A striking new image from the James Webb Space Telescope (JWST) reveals two dwarf galaxies locked in a dramatic gravitational encounter, connected by a luminous bridge of gas and dotted with clusters of newly formed stars. The interacting pair — NGC 4490 and NGC 4485, collectively cataloged as Arp 269 — lies roughly 24 million light-years from Earth.

Webb's infrared instruments, NIRCam and MIRI, provide an unprecedented view: individual stars are resolved and the fine structure of the gas flowing between the galaxies is visible, exposing regions of active star formation that earlier Hubble observations could not fully resolve.

The larger galaxy, NGC 4490, spreads across the left of the frame in a complex weave of dust and young stars, while its smaller companion, NGC 4485, glows toward the upper right. Between them stretches a bright bridge of gas and dust studded with blue-hued clusters of newborn stars set against the reddish glow of warm interstellar dust. Astronomers interpret this bridge as material transferred from one galaxy to the other during their close encounter, which has triggered waves of star formation along the connecting filament.

“Aside from the Milky Way’s own dwarf companions — the Large and Small Magellanic Clouds — this is the closest known interacting dwarf–dwarf system where astronomers have directly observed both a gas bridge and resolved stellar populations,” said officials from the European Space Agency (ESA).

Analysis suggests the two dwarfs swept past one another about 200 million years ago. During that encounter, NGC 4490 appears to have siphoned gas from NGC 4485, creating the visible bridge and fueling star formation episodes, some of which began as recently as 30 million years ago.

Why This Matters

Dwarf galaxies like NGC 4490 and NGC 4485 are low-mass, gas-rich and metal-poor systems that resemble the kinds of galaxies that populated the early universe. Studying their interactions and gas exchanges offers astronomers a nearby laboratory for understanding how the first galaxies grew and evolved through mergers and material transfer.

In short: Webb’s infrared view of Arp 269 delivers a star-by-star timeline of a cosmic encounter, revealing how collisions between small galaxies drive gas exchange and trigger bursts of star formation — a process that helped shape the universe’s earliest galaxies.

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