The first galaxies may have formed much earlier than previously thought, according to observations from the James Webb Space Telescope that are reshaping our understanding of early astronomy.
Researchers who use the powerful detector have now published papers in journals Astrophysical Journal Lettersdocumenting two unusually bright, very distant galaxies, based on data collected within days of Webb’s launch in July.
Their intense brightness points to two interesting features, astronomers at NASA press conference said Thursday.
The first is that these galaxies are very large, with as many low-mass stars as galaxies today, and they had to start forming 100 million years after the Big Bang, which occurred 13.8 billion years ago.
This is 100 million years earlier than the end of the so-called cosmic darkness, when the universe had only air and dark matter.
A second possibility is that they are made up of “Population III” stars, which have never been observed but are said to be made of only helium and hydrogen, the pre-heaviest elements.
Because these stars burn at extreme temperatures, the galaxies formed in them would not have to be very massive to account for the light Webb saw and could have formed later.
“We’re seeing very bright galaxies at this time, so we don’t know what’s going on here,” Garth Illingworth of the University of California at Santa Cruz told reporters.
The rapid discovery of these galaxies also contradicted the fact that Webb would need to search more space to find such galaxies.
“It’s surprising that there are so many that were created so quickly,” added physicist Jeyhan Kartaltepe of the Rochester Institute of Technology.
A lot of starlight
The two galaxies were found to have existed approximately 450 and 350 million years after the Big Bang.
The second of these, called GLASS-z12, now represents the light of a star never seen before.
When things are very far away from us, it takes a long time for their light to reach us, so looking at the distant universe is seeing the deep past.
When these galaxies are very far from the Earth, when their light reaches us, it has been stretched by the growth of the universe and moved to the infrared region of light.
Webb can detect infrared light at a much higher level than any previous instrument.
Illingworth, who co-authored the GLASS-z12 paper, told AFP that confusing the two competing concepts would be “a real challenge,” although the Population III concept was particularly interesting to him, as it would not require upgrading the existing species.
The teams hope to use Webb’s powerful telescopes – which analyze light from objects to reveal details – to determine the distances of galaxies, and better understand their formation.
The Atacama Large Millimeter/submillimeter Array (ALMA), a ground-based telescope in northern Chile, could also measure the mass of the two galaxies, which would help decide between the two theories.
“JWST has opened new frontiers, bringing us closer to understanding how it all began,” said Tommaso Treu of the University of California, Los Angeles, principal investigator on one of Webb’s programs.
© Agence France-Presse
