The neck of one of the Milky Way Galaxy’s spiral arms is a land of giants. Astronomers have discovered several monster star clusters there. And the clusters are dominated by some of the biggest and heaviest stars in the galaxy: red supergiants.

The clusters reside in the Scutum-Centaurus Arm — a lane of stars and gas clouds that curves around the galaxy. It spirals off the end of a “bar” of stars at the galaxy’s heart. The arm funnels gas toward the bar. The gas piles up, then splits into clumps that give birth to stars.

Those “clumps” include at least four red-supergiant star clusters — the only ones yet seen in the entire galaxy.

Red supergiant stars are much bigger and heavier than the Sun, and tens of thousands of times brighter. But they’re rare. In fact, these clusters and the space around them contain a large fraction of all the Milky Way’s red supergiants.

The clusters are quite young — no more than 20 million years old. Yet because the red supergiant stars are so massive, they’re already in the final stages of life, so they’re huge and brilliant. And soon, they’ll shine even brighter. Every red supergiant will explode as a supernova — depriving the clusters of their most impressive residents.

The clusters are in the constellation Scutum, which is in the south at nightfall, above teapot-shaped Sagittarius. Despite their brilliance, the clusters are veiled by clouds of dust, so they’re hidden from view.

Script by Damond Benningfield

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