Discovery of 'Big Wheel' challenges galaxy formation theories

Deep observations from the James Webb Space Telescope revealed an exceptionally large galaxy in the early universe. This cosmic giant, whose light travelled over 12 billion years to reach us, was named the "Big Wheel" by researchers. Their discovery was published in the scientific journal Nature Astronomy.

This gigantic disk galaxy existed within the first two billion years after the Big Bang, which means it formed when the universe was just 15 percent of its current age. This challenges what we know about how galaxies form.

What is a disk galaxy? It's a flat, rotating structure composed of stars, gas, and dust. As scientists describe, disk galaxies typically have distinct spiral arms extending outward from the dense central region. Our Milky Way galaxy is itself a disk galaxy, characterized by beautiful spiral arms wrapping around its center.

Studying disk galaxies such as the Milky Way and the newly discovered "Big Wheel" helps us understand how galaxies form, grow, and evolve over billions of years. This research is particularly important because understanding galaxies similar to ours can provide deeper insights into the cosmic history of our galactic home.

Until now, researchers believed that galactic disks form gradually over a long time: either through the smooth inflow of gas into galaxies from surrounding space or through mergers with smaller galaxies.

Typically, rapid collisions between galaxies would disrupt delicate spiral structures, transforming them into more chaotic shapes. However, "Big Wheel" managed to quickly reach a surprisingly large size without losing its characteristic spiral shape. This challenges long-held theories about the growth of giant galaxies.

Detailed observations by the Webb Telescope show that "Big Wheel" is comparable in size and rotational speed to the largest "super-spiral" galaxies in the contemporary universe. It is three times larger than comparable galaxies from that era and is one of the most massive galaxies observed in the early cosmos. Interestingly, despite being extremely large, "Big Wheel" actively grows at a rate similar to other galaxies at the same cosmic age.

As described by researchers in the article, "Big Wheel" is located in an extraordinarily crowded region of space where galaxies are packed closely together, ten times denser than in typical areas of the universe. This dense environment likely provided the ideal conditions for the rapid growth of the galaxy. It likely experienced collisions that were gentle enough to allow the galaxy to maintain its spiral disk shape. Additionally, the gas inflow into the galaxy must have been well-aligned with its rotation, allowing the disk to grow rapidly without disturbances. This is an ideal combination.

The discovery of a galaxy like "Big Wheel" was improbable. According to current galaxy formation models, scientists estimated less than a 2 percent chance of identifying such a structure in their study. They described the finding as unexpected, suggesting that its presence might be due to its location in an exceptionally dense region, which differs from typical cosmic environments, as noted in an interview with Science Alert.

Beyond its mysterious formation, the ultimate fate of "Big Wheel" is another intriguing issue. As scientists predict, given the dense environment, future collisions may significantly alter its structure, potentially transforming it into a galaxy comparable in mass to the largest observed in nearby clusters, such as Virgo.

"The discovery of 'Big Wheel' has unveiled another secret of the early universe, showing that our current models of galaxy evolution still require refinement," researchers said. With further observations and discoveries of massive, early galaxies like "Big Wheel," astronomers will be able to uncover more mysteries regarding how the universe built the structures we see today.