Milky Way’s ‘Yellowballs’ Confirmed as Infant Star Clusters

Between 2010 and 2015, citizen scientists scanning false-color images from NASA’s now-defunct Spitzer Space Telescope discovered something strange: globes of yellow light strewn about the Milky Way. The citizen scientists speculated the globes represented a step in star formation, and soon began referring to them as yellowballs. Now, six years later, another team of scientists says it can confirm the yellowballs are indeed clusters of infant stars. More specifically, they represent is the stars’ “in utero” phase.

Charles Kerton, Iowa State University/ NASA

Science News reported on the confirmatory study, which a team of scientists recently published in The Astrophysical Journal. The team had the citizen scientists collect 6,000 more yellowbubble locations, and found that up to 30 percent of a sampling of the collection contained 100,000-year-old stars. That is an incredibly young age for stars, which often live for billions of years. (Age depending, in part, on how eager they are to explode.)

Grace Wolf-Chase, an astronomer at the Planetary Science Institute in Naperville, Illinois, led the researchers. Wolf-Chase told Science News that she “think[s] of these as stars in utero” and that they exist in “cold environments before the stars are actually born.” The star-birth Wolf-Chase refers to is when a massive object has enough density to generate nucleosynthesis. I.e. sustained nuclear fusion reactions that make stars all…starry.

Charles Kerton, Iowa State University/ NASA

The scientists say they can confirm the yellowballs as embryonic stars by comparing them to existing catalogs of star clusters. (Stars are “born” in nebulae, which are unimaginably massive clouds of gas and dust; the clouds shrink under their own gravity, and eventually become so dense they initiate nucleosynthesis.)


The goal now, Wolf-Chase says, is to be able to pick out and study individual yellowballs. The astronomer and her colleagues will use the upcoming James Webb Space Telescope for that research; another space observatory, which, like Spitzer, has been built to survey the universe in (mostly) the infrared range of the electromagnetic spectrum. But that’s the only way to image faint, distant objects like these yellowballs. And colorizing the pictures seems to be just as much fun as coming up with names for the objects in them anyway.

Feature image: Rawpixel Ltd.

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