Free Astronomy Magazine January-February 2025

JANUARY-FEBRUARY 2025 ASTRO PUBLISHING T hese are two views of the same scene, each showing two over- lapping spiral galaxies, IC 2163 at left and NGC 2207 at right. The Hubble Space Telescope’s ultravio- let- and visible-light observation is above, and the James Webb Space Telescope’s mid-infrared light ob- servation is below. In Hubble’s image, the star-filled spiral arms glow brightly in blue, and the galaxies’ cores in orange. Both galaxies are covered in dark brown dust lanes, which obscures the view of IC 2163’s core at left. In Webb’s image, cold dust takes center stage, casting the galaxies’ arms in white. Areas where stars are still deeply embedded in the dust appear pink. Other pink regions may be objects that lie well behind these galaxies, including active supermassive black holes known as quasars. Turn your eye toward the bottom right of the Webb image. The largest, brightest pink region that glimmers with eight prominent diffraction spikes is a mini starburst — a location where many stars are forming in quick succession. The same region in the Hubble image appears as a bright blue cluster of stars. The lace-like holes in the white spiral arms of Webb’s images are often where supernovae exploded long ago. In the same regions, Hubble shows these areas are now popu- lated with newer stars. The black areas to upper right and lower left of the Hubble image do not contain any data. [NASA, ESA, CSA, STScI] decades, a high number compared to an average of one every 50 years in the Milky Way. Each supernova may have cleared space in their arms, rearranging gas and dust that later cooled, and allowed many new stars to form. To spot the star-forming “action se- quences,” look for the bright blue areas captured by Hubble in ultravi- olet light, and pink and white re- gions detailed mainly by Webb’s mid-infrared data. Larger areas of stars are known as super star clus- ters. Look for examples of these in the top-most spiral arm that wraps above the larger galaxy and points left. Other bright regions in the galaxies are mini starbursts — loca- tions where many stars form in quick succession. Additionally, the top and bottom “eyelid” of IC 2163, the smaller gal- axy on the left, is filled with newer star formation and burns brightly. What’s next for these spirals? Over many millions of years, the galaxies may swing by one another repeatedly. It’s possible that their cores and arms will meld, leaving behind completely reshaped arms, and an even brighter, cyclops-like “eye” at the core. Star formation will also slow down once their stores of gas and dust deplete, and the scene will calm. n