James Webb Space Telescope Feed Post

Firefly Sparkle Galaxy and Companions in Galaxy Cluster MACS J1423 (NIRCam Image)

Webb discerned distinct star clusters in the Firefly Sparkle galaxy, which existed 600 million years after the big bang - the first discovery of an actively forming galaxy as lightweight as the young Milky Way. The gravity of a massive foreground galaxy cluster has magnified and stretched Firefly Sparkle's star clusters into a line of bright sparks, giving it its name. For Webb to resolve a galaxy from so early in the universe, let alone to see its distinct components, is extraordinary. These clusters of star formation are the Firefly Sparkle galaxy’s building blocks. The analysis of the colors confirms that the star formation didn’t happen all at once, but was staggered over time, with each clump of stars at a different phase of formation or evolution. Another piece of evidence that the galaxy is still in the process of forming is that the projected actual shape of the galaxy shows its stars haven’t settled into a central bulge or thin, flattened disk. Other galaxies detected by Webb from this time period in the Universe’s history are much more massive than the Firefly Sparkle, which itself is more similar in mass to what our Milky Way’s might have been at this same stage of development. Read more: science.nasa.gov/missions/webb/found-first-actively-formi... Image credit: NASA, ESA, CSA, STScI, Chris Willott (NRC-Canada), Lamiya Mowla (Wellesley College), Kartheik Iyer (Columbia) Image description: Horizontal split down the middle. At left is a galaxy cluster showing thousands of overlapping objects at various distances spread across this field. The background is black. The galaxies’ colors vary, including white, pink, orange, and blue. Most galaxies appear as ovals or dots. Just above center is a bright white oversized oval, a supergiant elliptical galaxy. Immediately around it are many thin, long orange or pink arcs. These are background galaxies that have been stretched and distorted. To the bottom right is the outline of a small box. On the right side is a zoomed in view of this area. There are two smaller circles flanking a larger oval at the center. The central oval is labeled Firefly Sparkle galaxy. Within it is a long line, roughly pointing from bottom left to top right that contains 10 circular star clusters in pink, purple, and blue. The galaxy to the bottom left is labeled Companion 1 and looks like a bright red dot. At top right, Companion 2 is lighter red and surrounded by a red disk. Image & Description by NASA