Have you ever wondered what our Milky Way galaxy looked like in its early history? Astronomers using the Webb Space Telescope (JWST) have found another galaxy that is almost a mirror image of our childhood galaxy. It has the nickname “Bengal fire”. This is because there are about two dozen bright globular clusters orbiting it. There are also several dwarf galaxies absorbed by the galaxy.

The JWST view shows what the Spark looked like when the Universe was only four billion years old, or about a third of its current age. This means that this galaxy, like the Milky Way, began to form very early in cosmic history. If the sparkler is following the same growth path as the Milky Way through galactic mergers and acquisitions, then it must be evolving like the Milky Way. In about nine billion years, it may look very similar to our twin.

A distant, early proxy of our Milky Way

The sparkler lies in the direction of the Volan constellation (in the southern hemisphere of the sky). The redshift is quite far with z = 1.38. That’s about 9 billion light years, a few billion years after the Big Bang. Like the Milky Way, the Sparkler was not fully formed from space.

Both galaxies began as “extremely dense” matter (as clouds of neutral hydrogen) in the early universe. Think of them as the “seeds” of galaxies drawn together by their gravitational pull. Globular clusters were born in some of these clusters, possibly a little before the birth of the galaxy. This is why stars in some spherical galaxies are older than their own galaxies.

Then came the era of mergers and acquisitions, when the maturing Milky Way (and possibly Sparkler too) began cannibalizing neighboring dwarf galaxies. This is a big evolutionary step. At least half of our galaxy’s mass is likely to come from these mergers. Over time, all the material coalesced into a spiral disk where the Sun and many other stars exist today.

The future of Sparkler compared to the Milky Way

Will Sparkler follow the same evolutionary path as the Milky Way? From the JWST data it looks like that. Although currently only a small fraction of the Milky Way’s mass – about 3 percent – will change as it absorbs other smaller galaxies. Over time it will equal the mass of the Milky Way in the modern universe. This is very exciting because it gives astronomers a chance to understand what happened during the evolution of our galaxy.

“We are witnessing firsthand the formation of this galaxy as it forms its mass in the form of a dwarf galaxy and several globular clusters,” said Professor Duncan Forbes of Swinburne University in Australia.

He studied the galaxy and its clusters with Professor Aaron Romanowski of San Jose State University in California.

“We are excited about this unique opportunity to study both the formation of globular clusters and the formation of the Milky Way at a time when the universe is only 1/3 the age of its current age,” he said.

Forbes and Romanowsky used the JWST data to investigate the age and metallicity of various “glows” (compact sources) in and around the Sparkler Galaxy. The aim was to study the metallicity in the range of compact star clusters surrounding Sparkler. The scientists wanted to see if the spherical parts of the Milky Way were similar to younger versions.

Clues to the early history of Sparkler in its globular clusters

According to Romanovsky, JWST’s Sparkler observations could also answer several questions about globular clusters and their formation. “The origin of globular clusters is a long-standing mystery,” he said. “We are very excited that JWST can look back and see them in their youth.”

It turns out that the spark clusters bear a striking resemblance to some spherical parts of the Milky Way. A few have been seen to form very early, and the stars are quite metal-rich. This indicates a very rapid chemical enrichment process in the early universe.

A few clusters contained stars that were slightly older and metal-poor than other clusters. They probably belong to a low-mass satellite galaxy that Sparkler has absorbed. The scene is very reminiscent of the Milky Way’s history of convergence during its lifetime.

Additional data required

To better understand the evolutionary status of sparklers and their clusters, the two scientists say additional observations of similar clusters around other distant galaxies in the Universe are needed. This will help determine if Sparkler’s galaxy evolution is typical for a merger style (similar to the Milky Way). If not, then the details of early galaxy evolution, chemical enrichment, mass growth, and star cluster formation may need some revision.