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NASA’s Webb Telescope Sheds Light on Hidden Layers of Interstellar Dust and Gas

NASA’s Webb Telescope Sheds Light on Hidden Layers of Interstellar Dust and Gas
NASA/JPL-Caltech/Y. Kim (Univ. of Arizona/Univ. of Chicago). Cassiopeia A Inset: NASA, ESA, CSA, STScI, Danny Milisavljevic (Purdue University), Ilse De Looze (UGent), Tea Temim (Princeton University). Light Echoes Inset: NASA, ESA, CSA, STScI, J. Jencson (Caltech/IPAC)
  • PublishedJanuary 19, 2025

Centuries ago, the violent death of a massive star sent shockwaves through the cosmos, creating an extraordinary chain of events that scientists are only now beginning to unravel.

NASA’s James Webb Space Telescope (JWST) has revealed intricate details of interstellar dust and gas illuminated by the lingering echoes of this stellar explosion. These groundbreaking observations are reshaping how astronomers view the complex and mysterious structures of the interstellar medium.

When the core of a massive star collapsed, it unleashed a shockwave that tore the star apart. This catastrophic event also produced an intense pulse of X-rays and ultraviolet light. Now, 350 years later, that pulse has reached surrounding interstellar material, warming it and causing it to glow in infrared light—a phenomenon known as a light echo.

Webb’s advanced infrared imaging capabilities have captured these light echoes in astonishing detail, exposing the intricate structures of the interstellar medium. The telescope’s Near-Infrared Camera (NIRCam) revealed fine, sheet-like filaments and tightly wound magnetic “knots” within the glowing material. These formations, resembling the grain of polished wood, were previously invisible to astronomers.

“We were pretty shocked to see this level of detail,” said Jacob Jencson of Caltech, principal investigator of the study.

According to Josh Peek of the Space Telescope Science Institute, these findings suggest that dense, dusty regions throughout the galaxy may share similar internal structures, although this is the first time such details have been observed.

The observations provide a 3D view of the interstellar medium, much like a medical CT scan. Multiple images taken weeks apart allowed researchers to trace the motion of the glowing filaments, offering insights into their composition and how they interact with magnetic fields.

The focal point of these discoveries is the supernova remnant Cassiopeia A, located 11,000 light-years away. This region, studied previously by NASA’s Spitzer Space Telescope, was revisited by Webb to capture a more detailed view of the light echoes. The high-resolution images show the expansion of glowing gas and dust as the supernova’s radiation travels through space.

The data suggest that the filaments’ small-scale structures, about 400 astronomical units in size, may be influenced by interstellar magnetic fields. These findings also hint at the processes through which gas sheds its magnetic field, a critical step in star formation.

“This is going to completely change the way we think about the foundations of the cold interstellar medium,” said Peek during a press conference at the 245th American Astronomical Society meeting.

By observing the same regions over time, the team aims to map the 3D structure of interstellar dust and study how light echoes evolve.

The researchers are also using Webb’s Mid-Infrared Instrument (MIRI) to analyze the chemical makeup of the illuminated dust, looking for changes caused by the supernova’s radiation. This work may even reveal whether the smallest dust grains are destroyed in the process.

NASA Administrator Bill Nelson hailed Webb’s discoveries as a testament to the ingenuity and dedication of the international team behind the mission.

“Every image, every discovery, shows a portrait not only of the majesty of the universe but the power of the NASA team and the promise of international partnerships,” he said.

NASA and Space.com contributed to this report.

Written By
Joe Yans