James Webb's deep-field image reveals three of the earliest galaxies
Three of the earliest galaxies have been identified from the deep-field image captured by the James Webb Space Telescope. These galaxies were found to be extremely young and resembled a rare class of small galaxies called "green peas." Interestingly, the galaxy trio is seen as they were when the universe was about 5% of its current age of 13.8 billion years.
Why does this story matter?
To recall, the deep-field image is the first-ever image snapped by the James Webb telescope. It is the deepest and sharpest infrared image of the distant universe so far and thousands of galaxies can be seen in and behind the galaxy cluster named SMACS 0723. The recently discovered distant trio of galaxies was spotted behind the SMACS 0723 cluster.
What are the green pea galaxies?
Green pea galaxies were discovered in 2009. They are small galaxies, measuring about 5,000 light-years across, that's approximately 5% the size of the Milky Way. The green pea galaxy colors are unusual because a portion of their light comes from bright gas clouds. Unlike stars, which produce a rainbow-like spectrum of continuous color, these gases emanate light at specific wavelengths.
One of the galaxies might be the most chemically primitive
"And we see that they are young galaxies in every sense - full of young stars and glowing gas that contains few chemical products recycled from earlier stars," said Sangeeta Malhotra, a researcher at NASA's Goddard Space Flight Center. "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."
Webb also captured the spectra of the galaxies
Also, Webb's in-house Near-Infrared Spectrograph (NIRSpec) instrument captured the spectra of selected galaxies. For the first time, they were able to measure the level of oxygen in these galaxies from spectral information. Upon analysis, researchers discovered that the distant galaxies had striking similarities to the nearby green peas galaxies. The oxygen content of two of the galaxies was about 20% of the Milky Way.
