JWST is peering deep into the early galaxies of the universe, revealing something surprising: ScienceAlert
The first galaxies may have formed much earlier than thought, according to observations from the James Webb Space Telescope that are reshaping astronomy’s understanding of the early universe.
Researchers using the powerful observatory have now published their work in a journal Astrophysical Journal Letters, documenting two extremely brightextremely distant galaxies, based on data collected in the first few days since the Web went live in July.
Their extreme brightness points to two intriguing possibilities, astronomers said in a NASA press release Thursday.
The first is that these galaxies are very massive, with as many low-mass stars as galaxies today, and must have started forming 100 million years after Big bang which occurred 13.8 billion years ago.
That is 100 million years earlier than the currently held end of the so-called cosmic dark ages, when the universe contained only gas and Black matter.
Another possibility is that they consist of “Population III” stars, which have never been observed but are assumed to have been made only of helium and hydrogen, before heavier elements existed.
Because these stars burned so brightly at extreme temperatures, the galaxies made from them would not have to be so massive to account for the glow seen by Webb and could have formed later.
“We’re seeing galaxies so bright, so bright at this early age, we’re not sure what’s going on here,” Garth Illingworth of the University of California, Santa Cruz, told reporters.
The rapid discovery of galaxies also defied expectations that Webb would need to explore a much larger area to find such galaxies.
“It’s little surprise that there are so many that formed so early,” added astrophysicist Jeyhan Kartaltepe of the Rochester Institute of Technology.
The most distant starlight
The two galaxies were determined to have definitely existed approximately 450 and 350 million years after the Big Bang.
The second of these, called GLASS-z12, now represents the most distant star ever seen.
The farther the objects are from us, the longer it takes for their light to reach us, so looking into the distant universe means peering into the deep past.
Because these galaxies are so far from Earth, by the time their light reaches us, it has been stretched by the expansion of space and shifted into the infrared region of the light spectrum.
Webb can detect infrared light at far greater resolution than any instrument before it.
Illingworth, who co-authored the GLASS-z12 paper, told AFP that separating the two competing hypotheses would be “a real challenge”, although he found the idea of Population III more appealing because it would not require changing existing cosmological models.
The teams hope to soon use Webb’s powerful spectrographic instruments – which analyze light from objects to reveal their detailed properties – to confirm the galaxies’ distances and better understand their composition.
The Atacama Large Millimeter/submillimeter Array (ALMA), a ground-based telescope in northern Chile, could also help measure the masses of the two galaxies, which would help decide between the two hypotheses.
“JWST has opened a new frontier, bringing us closer to understanding how it all began,” summarized Tommaso Treu of the University of California, Los Angeles, principal investigator on one of the Webb programs.
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