The Webb Space Telescope has spotted six pinpricks of reddish-orange light that scientists say are actually galaxies as mature as the Milky Way—despite being billions of years younger.
The galaxies are seen as they looked about 500 million to 800 million years after the Big Bang, over 13 billion years ago. The presence of galaxies so early in the universe is not surprising, but the degree to which the galaxies are developed is throwing astronomers for a loop. Analysis of the image data is published today in Nature.
“These objects are way more massive than anyone expected,” said Joel Leja, an astronomer at Penn State, in a university release. “We expected only to find tiny, young, baby galaxies at this point in time, but we’ve discovered galaxies as mature as our own in what was previously understood to be the dawn of the universe.”
According to Leja, the galaxies’ apparent mass means cosmological models may need to be revised, as well as our understanding of how early galaxies formed. “My first thought was we had made a mistake and we would just find it and move on with our lives,” he said. “But we have yet to find that mistake, despite a lot of trying.”
Webb launched in December 2021 and has been releasing a steady stream of scientific imagery of the cosmos since July 2022. Many of Webb’s deep-field images have captured some of the most distant objects ever observed, namely galaxies in the early universe.
One of the imaged stars (in the bottom left corner of the above image) could be as full of stars as the Milky Way is today but is 30 times more compact, according to the team.
Given their apparent maturity, it may no longer be proper to refer to them as primordial. Followup observations of the galaxies (Leja suggests spectrum imaging) could reveal their actual distances and compositions.
More: Webb Telescope Spots Ancient Galaxy Built Like the Milky Way