Free Astronomy Magazine March-April 2025

18 pearance through a natural effect known as gravitational lensing. And when combined with the telescope’s specialization in high-resolution in- frared light, Webb delivered un- precedented new data about the galaxy’s contents. “Without the benefit of this gravita- tional lens, we would not be able to resolve this galaxy,” said Kartheik Iyer, a co-lead author and NASA Hub- ble Fellow at Columbia University in New York. “We knew to expect it based on current physics, but it’s sur- prising that we actually saw it.” Mowla, who spotted the galaxy in Webb’s image, was drawn to its gleaming star clusters, because ob- jects that sparkle typically indicate they are extremely clumpy and com- plicated. Since the galaxy looks like a “sparkle” or swarm of lightning bugs on a warm summer night, they named it the Firefly Sparkle galaxy. The research team modeled what the galaxy might have looked like if it weren’t stretched and discovered that it resembled an elongated rain- drop. Suspended within it are two star clusters toward the top and eight toward the bottom. “Our reconstruction shows that clumps of actively forming stars are by NASA/ESA/CSA Claire Blome Christine Pulliam F or the first time, NASA’s James Webb Space Telescope has de- tected and “weighed” a galaxy that not only existed around 600 mil- lion years after the big bang, but is also similar to what our Milky Way galaxy’s mass might have been at the same stage of development. Other galaxies Webb has detected at this time period are significantly more massive. Nicknamed the Firefly Sparkle, this galaxy is gleaming with star clusters — 10 in all — each of which researchers examined in great detail. “I didn’t think it would be possible to resolve a galaxy that existed so early in the universe into so many distinct components, let alone find that its mass is similar to our own galaxy’s when it was in the process of forming,” said Lamiya Mowla, co- lead author of the paper and an as- sistant professor at Wellesley College in Massachusetts. “There is so much going on inside this tiny galaxy, in- cluding so many different phases of star formation.” Webb was able to image the galaxy in crisp detail for two reasons. One is a benefit of the cosmos: A massive foreground galaxy cluster radically enhanced the distant galaxy’s ap- A ‘Milky Way’ in the young Universe