James Webb Space Telescope reveals thick cosmic dust of Sagittarius B2, the most most enormous star-forming cloud in the Milky Way — Space photo of the week

A stunning starscape at the center of the Milky Way
The James Webb Space Telescope's MIRI (Mid-Infrared Instrument) shows the Sagittarius B2 (Sgr B2) region in mid-infrared light. (Image credit: NASA, ESA, CSA, STScI, Adam Ginsburg, Nazar Budaiev, Taehwa Yoo; Image Processing: Alyssa Pagan (STScI))
Quick facts

What it is: Sagittarius B2 (Sgr B2) molecular cloud

Where it is: 25,000 light-years from Earth in the constellation Sagittarius

When it was shared: Sept. 24, 2025

Why it's so special: Stars in the Milky Way galaxy are born in huge molecular clouds. The most massive is Sagittarius B2, which is just a few hundred light-years from our the galaxy's central black hole (called Sagittarius A*). This black hole is much more bountiful than you might first think — it has 10% of the galactic center's gas, but accounts for about half of the region's ongoing star formation. Why star formation is so disproportionate within the galactic center region is a conundrum for scientists.

A stunning starscape captured by the James Webb Space Telescope

JWST's full-size image of the Sagittarius B2 star-forming cloud (Image credit: NASA, ESA, CSA, STScI, Adam Ginsburg (University of Florida), Nazar Budaiev (University of Florida), Taehwa Yoo (University of Florida); Image Processing: Alyssa Pagan (STScI))

The MIRI image is entirely different, revealing the region's dust clouds illuminated by its stars. It shows pink and purple clouds surrounded by very dark regions studded with stars. The JWST cannot see everything:. Even its infrared vision can't penetrate the densest clouds, which remain dark and opaque in the MIRI image. Within those regions, hidden from view, are the raw ingredients for stars.

A pink, purple and splotchy picture of clouds in outer space

Webb’s MIRI (Mid-Infrared Instrument) shows the Sagittarius B2 (Sgr B2) region in mid-infrared light, with warm dust glowing brightly. (Image credit: NASA, ESA, CSA, STScI, A. Ginsburg (University of Florida), N. Budaiev (University of Florida), T. Yoo (University of Florida). Image processing: A. Pagan (STScI))

Why Sagittarius B2 is so much more productive than the rest of the galactic center remains puzzling, but there are clues. On the right-hand side of the MIRI image is a very bright, red region known to be rich in molecular material. It could hold the key to why the cloud outpaces the star production of the entire galactic center, potentially reshaping theories of how galaxies grow and evolve. Scientists plan to use Webb's new data on Sagittarius B2 to figure out how long it has been forming stars and whether a specific event triggered its prolific activity.

For more sublime space images, check out our Space Photo of the Week archives.

Jamie Carter
Live Science contributor

Jamie Carter is a freelance journalist and regular Live Science contributor based in Cardiff, U.K. He is the author of A Stargazing Program For Beginners and lectures on astronomy and the natural world. Jamie regularly writes for Space.com, TechRadar.com, Forbes Science, BBC Wildlife magazine and Scientific American, and many others. He edits WhenIsTheNextEclipse.com.

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