Galaxies observed using James Webb telescope are most distant in known universe, astronomers say

Astronomers say they have discovered some of the earliest and most distant galaxies known to date using the James Webb Space Telescope.

An international team of researchers says using light captured by James Webb, the world's largest and most powerful space telescope launched a year ago, it was able to confirm four early galaxies dating back to less than 400 million years after the Big Bang.

Three of those galaxies are the most distant ever confirmed.

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University of California, Santa Cruz announced the news on Friday.

"We've discovered galaxies at fantastically early times in the distant universe," said Brant Robertson, professor of astronomy and astrophysics at UC Santa Cruz.

"With JWST (James Webb Space Telescope), for the first time we can now find such distant galaxies and then confirm spectroscopically that they really are that far away."

The telescope captured light, emitted by the galaxies more than 13.4 billion years ago, at a time when the universe was only two per cent of its current age, the researchers say.

They add that astronomers measure distance to a galaxy by determining its "redshift," or where distant objects appear to recede due to the expansion of the universe. As a result, light is stretched to longer and redder wavelengths through a phenomenon known as the Doppler effect.

Using spectroscopy, or separating light into its component wavelengths, the researchers were able to obtain more definitive redshift measurements.

Robertson says using these more precise redshift measurements, researchers can also figure out how many stars these galaxies have.

Star formation in these early galaxies, he says, would have started about 100 million years earlier than the age they were observed, meaning the earliest stars would have formed around 225 million years after the Big Bang.

"We are seeing evidence of star formation about as early as we could expect based on our models of galaxy formation," Robertson said.

He and the lead author of another paper on the results, Emma Curtis-Lake of the University of Hertfordshire in the United Kingdom, are scheduled to present their findings on Dec. 12 at a Space Telescope Science Institute conference in Baltimore.

With files from The Associated Press