Webb Telescope Discovered a Cosmic Dust Mill express
JWST/NIRSpec spectroscopy has revealed quasar UDS-27023 at redshift z=4.556. Its spectrum shows an exceptionally steep far-ultraviolet extinction (A1500/AV ≈ 8) and the absence of the 2175 Å bump, both hallmarks of a population dominated by small silicate grains. This indicates active generation and reprocessing of tiny dust around the quasar: shock waves and outflows can mechanically crush large grains, while dense winds provide a venue for direct condensation of silicates. Such steep-extinction quasars (SEQs) likely mark a fleeting phase where active galactic nuclei manufacture and spread fine dust, setting the stage for rapid grain growth in the interstellar medium and enriching the circumgalactic environment.
Using the James Webb telescope, astronomers peered into an ancient quasar—the dazzling heart of a galaxy where a giant black hole sucks in matter. It turns out it doesn't just destroy, but also creates: its powerful outflows and shock waves act like a true cosmic mill. They grind cosmic dust particles into the finest powder—just like ordinary sand, but pulverized to microscopic sizes.
And here's an unexpected twist: the telescope didn't spot the characteristic spectral feature that gives away carbon dust—which is almost everywhere. It seems this mill is selective: it only processes silicates, ignoring carbon.
🎯 The light from this quasar traveled 12.5 billion years to reach the telescope. We see it as it was just 1.3 billion years after the Big Bang.