Free Astronomy Magazine July-August 2024

31 JULY-AUGUST 2024 shows us that further investigation is required.” Webb’s observations of M82 in near- infrared light spur further questions about star formation, some of which the team hopes to answer with ad- ditional data gathered with Webb, including that of another starburst galaxy. Two other papers from this team characterizing the stellar clus- ters and correlations among wind components of M82 are almost fi- nalized. In the near future, the team will have spectroscopic observations of M82 from Webb ready for their analysis, as well as complementary large-scale images of the galaxy and wind. Spectral data will help as- tronomers determine accurate ages for the star clusters and provide a sense of timing for how long each phase of star formation lasts in a starburst galaxy environment. On a broader scale, inspecting the activity in galaxies like M82 can deepen astronomers’ understanding of the early universe. “Webb’s ob- servation of M82, a target closer to us, is a reminder that the telescope excels at studying galaxies at all dis- tances,” said Bolatto. “In addition to looking at young, high-redshift gal- axies, we can look at targets closer to home to gather insight into the processes that are happening here – events that also occurred in the early universe.” S tarburst galaxy M82 was observed by the Hubble Space Tele- scope in 2006, which showed the galaxy’s edge-on spiral disk, shredded clouds, and hot hydrogen gas. The James Webb Space Telescope has observed M82’s core, capturing in unprecedented detail the structure of the galactic wind and characterizing indi- vidual stars and star clusters. The Webb image is from the tele- scope’s NIRCam (Near-Infrared Camera) instrument. The red filaments trace the shape of the cool component of the galactic wind via polycyclic aromatic hydrocarbons (PAHs). PAHs are very small dust grains that survive in cooler temperatures but are de- stroyed in hot conditions. The structure of the emission is similar to that of the ionized gas, suggesting PAHs may be replenished from cooler molecular material as it is ionized. [NASA, ESA, CSA, STScI, Alberto Bolatto (UMD)] quent supernovae, is being launched and in- fluencing its surround- ing environment. By resolving a central section of M82, scien- tists could examine where the wind origi- nates, and gain insight on how hot and cold components interact within the wind. Webb’s NIRCam instrument was well-suited to trace the structure of the galactic wind via emission from sooty chemical molecules known as polycyclic aromatic hydrocarbons (PAHs). PAHs can be considered as very small dust grains that survive in cooler temperatures but are de- stroyed in hot conditions. Much to the team’s surprise, Webb’s view of the PAH emission highlights the galactic wind’s fine structure – an aspect previously unknown. De- picted as red filaments, the emission extends away from the central re- gion where the heart of star forma- tion is located. Another unantici- pated find was the similar structure between the PAH emission and that of hot, ionized gas. “It was unexpected to see the PAH emission resemble ionized gas,” said Bolatto. “PAHs are not supposed to live very long when exposed to such a strong radiation field, so perhaps they are being replenished all the time. It challenges our theories and ! historically been obscured. Looking closer toward the center, small specks depicted in green denote concentrated areas of iron, most of which are supernova remnants. Small patches that appear red sig- nify regions where molecular hy- drogen is being lit up by a nearby young star’s radiation. “This image shows the power of Webb,” said Rebecca Levy, second author of the study at the University of Arizona in Tucson. “Every single white dot in this image is either a star or a star cluster. We can start to distinguish all of these tiny point sources, which enables us to acquire an accurate count of all the star clusters in this galaxy.” Looking at M82 in slightly longer in- frared wavelengths, clumpy tendrils represented in red can be seen ex- tending above and below the gal- axy’s plane. These gaseous streamers are a galactic wind rushing out from the core of the starburst. One area of focus for this research team was understanding how this galactic wind, which is caused by the rapid rate of star formation and subse-