Distant Milky Way-like galaxy is older than we thought possible

Astronomers have spotted the earliest barred spiral galaxy yet. It is the same type of galaxy as our Milky Way, but it dates back to when the universe was just 2 billion years old, earlier than was thought possible.

Such galaxies have a distinctive bar-shaped structure in their centre made of stars, from which spiral arms stretch out.

About two-thirds of all spiral galaxies, including the Milky Way, have a prominent stellar bar filled with infant stars. Cosmic formation models have suggested that these galaxies only started forming some 4 billion years after the big bang. Now, Luca Costantin at the Spanish Astrobiology Centre and his colleagues have found an even older one.

The researchers spotted the oddity in data from the James Webb Space Telescope’s Cosmic Evolution Early Release Science (CEERS) survey, which has captured new images of thousands of very distant galaxies.

“It looked a bit weird to me,” says Costantin. “We were not able to classify its shape at first.”

By cross-referencing with data from the Hubble Space Telescope, the researchers identified it as a barred spiral galaxy, which they named ceers-2112.

The galaxy’s light has been travelling since 2 billion years after the big bang, which happened about 13.7 billion years ago. That makes ceers-2112 the most distant barred spiral galaxy ever discovered.

Simulations also suggest that the galaxy would have grown to the size of the Milky Way by 4 billion years after the big bang. “If we go back in time, the Milky Way may have looked like ceers-2112,” says Costantin, who says these observations could help us improve galaxy formation models and understand how the Milky Way and other barred spiral galaxies evolved in the early universe.

“Understanding and finding galaxies like the one we found is very important,” says Costantin. “It’s a way to look back in time the story of our galaxy and ultimately our origins.”