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<\/figure>\n\n\n\nGreen pea galaxies were discovered and named in 2009 by volunteers taking part in\u00a0Galaxy Zoo, a project where citizen scientists help classify galaxies in images, starting with those from the\u00a0Sloan Digital Sky Survey. Peas stood out as small, round, unresolved dots with a distinctly green shade, a consequence of both the colors assigned to different filters in the survey\u2019s composite images and a property of the galaxies themselves.<\/p>\n\n\n\n
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<\/a>Green pea galaxy colors are unusual because a sizable fraction of their light comes from brightly glowing gas clouds. The gases emit light at specific wavelengths \u2013 unlike stars, which produce a rainbow-like spectrum of continuous color. Peas are also quite compact, typically only about 5,000 light-years across or about 5% the size of our Milky Way galaxy.<\/p>\n\n\n\n
\u201cPeas may be small, but their star-formation activity is unusually intense for their size, so they produce bright ultraviolet light,\u201d said Keunho Kim, a postdoctoral researcher at the University of Cincinnati and a member of the analysis team. \u201cThanks to ultraviolet images of green peas from Hubble and ground-based research on early star-forming galaxies, it\u2019s clear that they both share this property.\u201d<\/p>\n\n\n\n
In July 2022, NASA and its partners in the Webb mission released\u00a0the deepest and sharpest infrared image of the distant universe yet seen, capturing thousands of galaxies in and behind a cluster known as SMACS 0723. The cluster\u2019s mass makes it a gravitational lens, which both magnifies and distorts the appearance of background galaxies. Among the faintest galaxies behind the cluster were a trio of compact infrared objects that looked like they could be distant relatives of green peas. The most distant of these three galaxies was magnified by about 10 times, providing a significant assist from nature on top of the telescope\u2019s unprecedented capabilities.<\/p>\n\n\n\n
Webb did more than image the cluster \u2013 its\u00a0Near-Infrared Spectrograph\u00a0(NIRSpec) instrument\u00a0also captured the spectra of selected galaxies in the scene. When Rhoads and his colleagues examined these measurements and corrected them for the wavelength stretch resulting from the expansion of space, they saw characteristic features emitted by oxygen, hydrogen, and neon line up in a stunning resemblance to those seen from nearby green peas.<\/p>\n\n\n\n Additionally, the Webb spectra made it possible to measure the amount of oxygen in these cosmic dawn galaxies for the first time.<\/p>\n\n\n\n As stars produce energy, they transmute lighter elements like hydrogen and helium into heavier ones. When stars explode or lose their outer layers at the ends of their lives, these heavier elements become incorporated into the gas that forms the next stellar generations, and the process continues. Over cosmic history, stars have steadily enriched the universe.<\/p>\n\n\n\n Two of the Webb galaxies contain oxygen at about 20% of the level in our Milky Way. They resemble typical green peas, which nevertheless make up less than 0.1% of the nearby galaxies observed by the Sloan survey. The third galaxy studied is even more unusual.<\/p>\n\n\n\n \u201cWe\u2019re seeing these objects as they existed up to 13.1 billion years ago, when the universe was about 5% its current age,\u201d said Goddard researcher Sangeeta Malhotra. \u201cAnd we see that they are young galaxies in every sense \u2013 full of young stars and glowing gas that contains few chemical products recycled from earlier stars. Indeed, one of them contains just 2% the oxygen of a galaxy like our own and might be the most chemically primitive galaxy yet identified.\u201d<\/p>\n\n\n\n NIRSpec was built for ESA (European Space Agency) by Airbus Industries. Its array of nearly half a million microshutters \u2013 tiny doors that can be opened or closed to admit or block light \u2013 allow it to capture spectra of up to 100 individual objects at a time. The microshutter array and detector subsystems were fabricated by NASA.<\/p>\n\n\n\n The James Webb Space Telescope, an international mission led by NASA with its partners ESA and CSA (Canadian Space Agency), is the world’s premier space science observatory. NASA Headquarters oversees the mission for the agency\u2019s Science Mission Directorate. NASA\u2019s Goddard Space Flight Center manages Webb for the agency and oversees work on the mission performed by the Space Telescope Science Institute, Northrop Grumman, and other mission partners. In addition to Goddard, several NASA centers contributed to the project, including the agency\u2019s Johnson Space Center in Houston, Jet Propulsion Laboratory in Southern California, Marshall Space Flight Center in Huntsville, Alabama, Ames Research Center in California\u2019s Silicon Valley, and others.<\/p>\n\n\n\n We recommend you: Moon scientists hail Artemis opportunities while still learning from Apollo<\/a><\/p>\n\n\n\n<\/figure>\n\n\n\n