JWST’s Early Release Observations (EROs) beautifully demonstrate JWST’s promise in characterizing the universe at Cosmic Dawn. A recent survey of distant galaxies captured by NASA’s James Webb Space Telescope reveals that they are remarkably similar to “green peas,” a rare class of small galaxies in our cosmic backyard and very young.
Green pea galaxies were discovered and named in 2009 by volunteers participating in Galaxy Zoo. In this project, citizen scientists are helping classify galaxies in images, starting with those from the Sloan Digital Sky Survey. Small, rounded, unresolved dots of a certain green hue were distinguished as peas in the composite images of the study and a feature of the galaxies themselves.
Because a significant portion of the light in green pea galaxies comes from brilliantly blazing gas clouds, these galaxies have distinctive colors. Unlike stars, which produce a rainbow-like spectrum of continuous colors, gases emit light at specific wavelengths. Peas are typically only 5,000 light-years across, or about 5% the size of our Milky Way galaxy. They are also relatively small.
Keunho Kim, a postdoctoral researcher at the University of Cincinnati and member of the analysis team, said: “Peas may be small, but their star-forming activity is unusually intense for their size, so they produce bright ultraviolet light. Thanks to Hubble’s ultraviolet images of green peas and ground surveys of early star-forming galaxies, it’s clear they both share this trait.”
James Rhoads, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said: “With detailed chemical fingerprints of these early galaxies, we see that they contain perhaps the most primitive galaxy yet identified. At the same time, we can connect these galaxies from the beginning of the Universe with similar galaxies nearby, which we can map in much greater detail. can study.”
Stars convert lighter elements such as hydrogen and helium into heavier elements as they generate energy. These heavier elements are integrated into the gas that creates subsequent stellar generations after stars burst or shed their outer layers at the end of their lives, continuing the process. Throughout the history of the universe, stars have steadily improved it.
Two of the Webb galaxies had oxygen levels about 20% lower than those of the Milky Way. Despite making up less than 0.1% of the closest galaxies seen by the Sloan survey, they resemble regular green peas. In fact, the oddity is present in the third galaxy analyzed.
Goddard researcher Sangeeta Malhotra said: “We see these objects as they existed until 13.1 billion years ago, when the universe was about 5% of its current age. And we see that they are, by all accounts, young galaxies – full of young stars and glowing gas that contains few chemicals recycled from previous stars. Indeed, one of them contains only 2% of the oxygen of a galaxy like ours and is perhaps the most chemically primitive galaxy yet identified.”
- James E. Rhoads, Isak GB Wold et al. Finding Peas in the Early Universe with JWST. The Astrophysical Journal Letters. DOI 10.3847/2041-8213/acaaf