Free Astronomy Magazine May-June 2023

38 MAY-JUNE 2023 ASTRO PUBLISHING T he spiral arms of NGC 7496, one of a total of 19 galaxies targeted for study by the Physics at High An- gular resolution in Nearby Galaxies (PHANGS) collaboration, are filled with cavernous bubbles and shells overlapping one another in this image from Webb’s Mid-Infrared In- strument (MIRI). These filaments and hollow cavities are evidence of young stars releasing energy and, in some cases, blowing out the gas and dust of the interstellar medium sur- rounding them. [NASA, ESA, CSA, Janice Lee (NOIRLab). Image process- ing: Joseph DePasquale (STScI)] The team is studying a diverse sam- ple of 19 spiral galaxies, and in Webb’s first few months of science operations, observations of five of those targets – M74, NGC 7496, IC 5332, NGC 1365, and NGC 1433 – have taken place. The results are al- ready astounding astronomers. “The clarity with which we are seeing the fine structure certainly caught us by surprise,” said team member David Thilker of Johns Hopkins University in Baltimore, Maryland. “We are directly seeing how the en- ergy from the formation of young stars affects the gas around them, and it’s just remarkable,” said team member Erik Rosolowsky of the University of Alberta, Canada. The images from Webb’s Mid-In- frared Instrument (MIRI) reveal the presence of a network of highly structured features within these galaxies – glowing cavities of dust and huge cavernous bubbles of gas that line the spiral arms. In some re- gions of the nearby galaxies ob- served, this web of features appears built from both individual and over- lapping shells and bubbles where young stars are releasing energy. “Areas which are completely dark in Hubble imaging light up in exquisite detail in these new infrared images, allowing us to study how the dust in the interstellar medium has ab- sorbed the light from forming stars and emitted it back out in the in- frared, illuminating an intricate net- work of gas and dust,” said team member Karin Sandstrom of the