Strange Green Peas Galaxies

On a quest to find Green Peas

A team of astronomers has discovered a group of rare galaxies called the “Green Peas” with the help of citizen scientists working through an online project called Galaxy Zoo. The finding could lend unique insights into how galaxies form stars in the early universe.

The galaxies are named Green Peas, because they appear small and green. “These are among the most extremely active star-forming galaxies we’ve ever found,” said Carolin Cardamone, an astronomy graduate student at Yale and lead author of the paper.
Of the one million galaxies that make up Galaxy Zoo’s image bank, the team found only 250 Green Peas. “No one person could have done this on their own,” Cardamone said. “Even if we had managed to look through 10,000 of these images, we would have only come across a few Green Peas and wouldn’t have recognized them as a unique class of galaxies.”

The galaxies, which are between 1.5 billion and 5 billion light years away, are 10 times smaller than our own Milky Way galaxy and 100 times less massive. But surprisingly, given their small size, they are forming stars 10 times faster than the Milky Way.

“They’re growing at an incredible rate,” said Kevin Schawinski, a postdoctoral associate at Yale and one of Galaxy Zoo’s founders. “These galaxies would have been normal in the early universe, but we just don’t see such active galaxies today. Understanding the Green Peas may tell us something about how stars were formed in the early universe and how galaxies evolve.”

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