Three high-redshift galaxies were discovered by astronomers with the NASA/ESA/CSA James Webb Space Telescope. They have remarkable similarities to green pea’ galaxies which are a very rare type of small galaxies within the local Universe.
Three faint galaxies are shown (circled), captured by the Webb deep image of the galaxy group SMACS J0723.3-7323. These properties, which look very similar to the rare and small galaxies known as green peas that can be found closer to us, show remarkable similarities. Image credit: NASA / ESA / CSA / STScI.
Volunteers who took part in Galaxy Zoo in 2009 discovered and named green pea galaxies. This project allows citizens to help categorize galaxies using images.
These galaxies were small and round with unresolved points. This was due to both the color assigned to the different filters in survey’s composite photos as well as the property of the galaxies.
Because brightly glowing gases clouds are a large part of the light that gives green pea color, it is unusual.
Gases emit light at certain wavelengths, unlike stars which create a continuous rainbow of color.
Also, green pea galaxies can be quite small. They are typically about 5,000 light years across and about 5% larger than our Milky Way Galaxy.
According to Dr. Keunho, a University of Cincinnati postdoctoral researcher, “Peas are small but their star formation activity is uncommonly intense for them size so they emit bright ultraviolet light.”
It’s evident that both have this property, thanks to Hubble’s ultraviolet photos of greenpeas and ground-based research into early star-forming galaxies.
Webb captured the sharpest, most detailed infrared images of the distant Universe in July 2022. He took thousands of photos behind and within a cluster of galaxy known as SMACS J0723.3-7328.
Because of its mass, the cluster acts as a gravitational lens that magnifies or distorts background galaxies.
A trio of small infrared objects, which looked distantly like green peas, were among the galaxies with the weakest clusters.
This magnified the most distant galaxies by approximately 10x, which was a substantial help from nature in addition to the telescope’s unparalleled capabilities.
Webb’s Near-Infrared Spectrograph, (NIRSpec), also captures the spectra selected galaxies within the SMACS field J0723.3-7327.
These measurements were examined by Dr. Kim with his colleagues and adjusted for wavelength stretching due to the expansion of space. They saw the characteristic features emitted from neon, hydrogen and oxygen resembling those from green peas.
The Webb spectra also made it possible for the first-time to determine the oxygen content of these Cosmic Dawn galaxies.
Stars produce energy by transforming lighter elements such as hydrogen and helium to heavier ones.
These heavier elements are incorporated in the gas which forms new stellar generations as a result of stars exploding or losing their outer layers.
Stars have continuously enriched the Universe throughout cosmic history.
The oxygen levels in two of the Webb galaxies are about 20% less than the Milky Way’s.
These galaxies look a lot like green peas. However, they make up only 0.1% of nearby galaxies as observed by Sloan Survey.
Even more bizarre is the third galaxy that was studied.
According to Dr. Sangeeta Alhotra (an astronomer at NASA’s Goddard Space Flight Center), “We are seeing these objects in the way they were up until 13.1 billion years before our current time,” she said.
We see they are young galaxies, full of glowing gas and young stars.
In fact, they contain only 2% of the oxygen in a galaxy similar to ours and could be the most primitive chemically-chemically identified galaxy.”
These results are available in Astrophysical Journal Letters.
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James E. Rhoads The authors and others. 2023. JWST: Finding Peas in Early Universe ApJL 942, L14; doi: 10.3847/2041-8213/acaaaf