Galaxies may have been partially responsible for the “reionization” of the universe.
The galaxies that helped transform the early universe may have been small, round, and green.
Astronomers using the James Webb Space Telescope noticed the Green Pea galaxy 13.1 billion years ago . Spotted just 700 million years after the Big Bang, these greenish-green spots could have triggered one of the biggest transformations in cosmic history, astronomers said at a Jan. 9 news conference in Seattle at the annual meeting of the American Astronomical Society.
The green pea first appeared in 2009 in images from the Sloan Digital Sky Survey, an ambitious project to map much of the sky. Citizen Science volunteers gave the objects their colorful names. Their greenish hue is due to the fact that most of their light comes from glowing gas clouds rather than directly from the stars.
These galaxies are rare in the modern universe. Astronomers believe that those that do exist are analogs of galaxies that were more numerous in the early universe.
“They’re a bit like living fossils,” said astrophysicist James Rhodes of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Lamitria, if you will,” referring to a fish that was thought to be extinct until it wasn’t appeared off the coast of South Africa in 1938.
These galaxies let in much more ultraviolet light, which can strip electrons from atoms, than ordinary galaxies. Thus, the green pea, dating to the first billion years or so of the universe, could be partially responsible for a dramatic and mysterious cosmic transition called reionization, when most of the hydrogen atoms in the early universe electrons were removed.
In the first image, JWST , published in July 2022, three ancient green peas appeared. The objects appear red in JWST’s infrared light, but the wavelengths of light they emit are the same as the previously discovered Green Pea. Conclusions were also published in Astrophysical Journal Letters January 1.
“This helps us explain how the universe reionized,” Rhodes said. “I think that’s an important piece of the puzzle.”
