The James Webb Space Telescope (JWST) has discovered more than 1,000 galaxies hidden in the early universe that bear an uncanny resemblance to our own Milky Way.
Shaped like warped vinyl and with delicate spiral arms, the Milky Way doppelganger was discovered by JWST more than 10 billion years ago in the cosmic past, when violent galactic mergers made it thought impossible for such fragile galaxies to exist in such large numbers.
But new research suggests that disk galaxies are 10 times more common in the early universe than astronomers previously thought. This strange discovery joins other discoveries by JWST that deepen the mystery of how giant galaxies, and the associated possibility of life, first flourished in the universe. The researchers published their findings on September 22 in the Astrophysical Journal.
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“For more than 30 years, it was thought that these disk galaxies were rare in the early universe because galaxies frequently experience violent collisions,” Leonardo Ferreira, an astronomer at the University of Victoria in Canada and lead author of the study, said in a statement. “The fact that JWST has found so many disk galaxies is another testament to the power of this instrument, and that galactic structure formed early in the universe, much earlier in fact than anyone expected.”
Most theories of galaxy formation suggest that it began 1 to 2 billion years after the beginning of the universe, when early star clusters transformed into dwarf galaxies. These dwarf galaxies then began to cannibalize each other, setting off a free-wheeling series of violent galactic mergers that eventually (10 billion years later) gave rise to massive galaxies like our own.
The Milky Way is a disk galaxy: with its spiral arms and squashed sombrero shape, it’s one of the most common types of galaxy in the universe today. But in earlier times, when the universe was smaller and packed with dwarf galaxies, astronomers long thought that galaxies like our own would quickly become distorted in shape.
But by observing with JWST from 9 to 13 billion years ago, astronomers found that of the 3,956 galaxies they discovered, 1,672 were disk galaxies like our own, many of which existed when the universe was only a few billion years old.
“Using the Hubble Space Telescope, we thought that disk galaxies were largely absent until the universe was about six billion years old,” Christopher Conselice, professor of extragalactic astronomy at the University of Manchester and co-author of the study, said in a statement. “These new results from JWST push the date for the formation of galaxies like the Milky Way back to the beginning of the universe.”
“This means that most stars exist and form inside these galaxies, completely changing our understanding of how galaxy formation occurs,” he added. “Based on our findings, astronomers will have to rethink their understanding of the formation of the first galaxies and the evolution of galaxies over the past 10 billion years.”
Given that we ourselves exist in a disk galaxy, astronomers have generally assumed that the conditions must be right for life to arise there — and if so, life may have emerged in the universe earlier than originally thought.