Generations of Stars Shape Their Galaxies, Webb Images Reveal

An ambitious project to image the face of 19 stunning spiral galaxies is well underway. A new publication showcases dramatic James Webb Space Telescope observations of five of these spirals, known by their call numbers: NGC 1365, NGC 7496, NGC 628, NGC 1433, and IC 5332. The views are already shedding light on the ways in which newborn stars shape the galaxies they reside in.

In these images, Webb captures the warm infrared glow of starbirth and the dust that shrouds it, especially tiny grains known as polycyclic aromatic hydrocarbons. Stellar embryos nest in an intricate jumble of filaments, shells, and bubbles, structures that are testament to the impact of previous stellar generations.

The images above are sorted by the strength of their stellar nurseries: NGC 1365 is bursting with new stars, while IC 5332 is far more sedate.
Science: NASA / ESA / CSA / Janice Lee (NOIRLab); Image processing: Alyssa Pagan (STScI), Joseph DePasquale (STScI) & Judy Schmidt

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The images join an already immense — and still-growing dataset — known as the Physics at High Angular resolution in Nearby Galaxies (PHANGS) program. PHANGS operates across several major observatories to understand stars’ influence within nearby galaxies (“nearby” is relative, meaning tens of millions of light-years away). Across all 19 spirals, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile has already captured 12,000 star-forming clouds, the Hubble Space Telescope has imaged 10,000 fully formed star clusters, and the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (also in Chile) has collected data on 20,000 star-blown bubbles.

Webb observations have become a crucial piece of this story, enabling astronomers to examine star formation on scales from tens to hundreds of light-years. The images therein reveal stars before they’re born — and before they’ve had a chance to destroy their natal homes — while they’re still embedded in dusty cocoons.

“We are directly seeing how the energy from the formation of young stars affects the gas around them, and it’s just remarkable,” says team member Erik Rosolowsky of the University of Alberta, Canada.

Ultimately, these images — and the others coming down the pike — will help astronomers calculate the timescales on which stars form, which will in turn shed light on the physical processes at work, such as turbulence and magnetic fields.

This set of five images showcases diverse properties: On one end, there’s NGC 1365, a barred galaxy bursting with new stars. It has lots of gas to fuel star formation and a strong spiral pattern. On the other end, there’s delicately shaped IC 5332, which has little gas; it has settled into a more sedate stage of star formation.

These first results are published as 21 research studies in a special issue of the Astrophysical Journal Letters. There’s much more to come as Webb continues to work on imaging all 19 galaxies amongst all its other planned targets.

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