Citizen Scientists Discover a new Feature in Star Formation: “Yellowballs”

Citizen Scientists Discover a new Feature in Star Formation: “Yellowballs”

AI is often touted as being particularly good at finding patterns among tons of data. But humans are also very good at pattern recognition, especially when it comes to visual images. Citizen science efforts around the world are capitalizing on this fact, and recent results from the Milky Way Project on Zooinverse show how effective it can be. The project’s volunteer team identified 6,176 yellowballs, a phase star clusters go through in their early years. This discovery helps scientists better understand the formation of these clusters and how they will eventually grow into individualized stars.

This is not the first time these features have been explored. The search actually began in 2011 with a relatively harmless message on a message board for the Milky Way Project: “Any ideas what these bright yellow fuzzy objects are?” became known. A catalog of these objects has grown in recent years, and the results of citizen science endeavors are occasionally peer-reviewed.

NASA video describing the Yellowballs citizen scientists found.
Photo credit: ScienceAtNASA YouTube Channel

These efforts have resulted in a much better understanding of what these unique astronomical features actually are. Yellowballs themselves are actually not yellow, at least not what we would normally perceive as yellow. They are only yellow in infrared images captured by the Spitzer Space Telescope and analyzed as part of the project. What the color yellow represents in the infrared images is dust and traces of organic compounds that absorb some of the infrared light.

It appears that young stars create this yellowing effect by heating the gas and dust that surround them in their early stages. Yellowballs appear to form in the first 100,000 years of a star’s life. Interestingly, it doesn’t seem to matter what size star is ultimately created in the cluster. Around 20% of the cataloged yellowballs led to “massive” stars with about ten times the mass of the sun.

A Spitzer picture with the yellow balls circled.
Photo credit: Charles Keaton, Iowa State University / NASA / Spitzer

Yellowballs themselves are quite massive, however. They start out about a light year in diameter, but expand to as much as 10 light years over the course of millions of years as they surround larger stars. When they reach this stage, they are more commonly referred to as “blisters” and are no longer as yellow. They expand to a wavelength that looks redder with Spitzer’s infrared collector.

No matter what color they are, these yellow spheres are a new chain in the connection between early star-forming regions and the stars they ultimately lead to. Further study will allow scientists to link the properties of these dense clouds to the types of stars they ultimately make up in, cementing the link between a star’s birth and its eventual composition. Sounds like more work for citizens and professional scientists.

Learn more:
PSI – “Yellowballs” offer new insights into star formation
Futurism – Citizen Scientists Guide Astronomers to the Source of the Yellowballs
EOS – The “Yellowball” catalog and the Citizen Science that helped define it

Mission statement:
Example of a yellowball (left) and a bubble (right)
Photo credit: NASA / JPL-Caltech

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