Mystery Galaxy Unveils Secrets of the Milky Way’s History

Back to Article List

The Firefly Sparkle Galaxy is the inaugural Milky Way-sized galaxy to be discovered while it is still in the process of developing.

Gravitational lensing (a phenomenon wherein faraway objects are enlarged or elongated by the gravity of a massive object along their line of sight) is among astronomers’ most valuable observational techniques. In a study published earlier this month, a team of astronomers and the James Webb Space Telescope (JWST) utilized this method to their benefit to identify and analyze an extraordinary discovery — a young, light-weight, early Milky Way emulator that is still actively developing.

This galaxy existed at a time when the universe was merely 600 million years old — just 5 percent of its current age. What renders this specific galaxy so remarkable is that the majority of galaxies identified during this era are significantly more massive. Another striking characteristic of this galaxy is that it harbors 10 dazzling star clusters, which inspired the galaxy’s charming name: the Firefly Sparkle Galaxy. 

“I didn’t believe it would be feasible to resolve a galaxy that existed so early in the universe into so many separate components, much less discover that its mass is akin to our own galaxy’s during its formation,” stated Lamiya Mowla, co-lead author of the research and an assistant professor at Wellesley College in Massachusetts, in a press statement. “There is an incredible amount happening inside this tiny galaxy, including various stages of star formation.” 

Reversing the Process

The Firefly Sparkle was previously photographed by the Hubble Space Telescope and Keck Observatory, but was later examined utilizing the combined capabilities of gravitational lensing and multi-wavelength data from JWST’s Canadian NIRISS Unbiased Cluster Survey (CANUCS). The significant lens effect was due to the enormous galaxy cluster named MACS J1423.8 + 2404, which is located between us and the Firefly Sparkle.

“Without the advantage of this gravitational lens, we would not be able to distinguish this galaxy,” noted Kartheik Iyer, a co-lead author of the study, in a press statement. “We expected it based on established physics, but it’s remarkable to see it.”

In the paper presented by the team, published in Nature on December 11, they devised a model to “reverse” the visual distortions caused by the lensing. It turns out the original shape of the Firefly Sparkle resembles an elongated raindrop; its stars have not yet organized into either a central bulge or a flat disk. In simpler terms, the galaxy is still very much in the process of developing. 

Sparking Wonders

The 10 separate star clusters exhibit various hues of pink, purple, and blue. This suggests that the stars within them are at different ages and formed at different periods — a conclusion supported by spectral analysis. “Each cluster of stars is experiencing a separate phase of creation or evolution,” remarked Chris Willow, a co-author and the principal investigator of the observation program.

The researchers have also identified that the Firefly Sparkle possesses two companion galaxies (with equally delightful names of Firefly-Best Friend and Firefly-New Best Friend) that are simply “hanging around,” as stated in the press release. One is merely 6,500 light-years from the Firefly Sparkle while the other is 42,000 light-years distant. The interactions among the three systems are essential for triggering star formation, causing the gases to condense, cool, and form clumps.

Astronomers remain uncertain about how the Firefly Sparkle will progress over the next few billion years. However, during the cosmic epoch corresponding to the observations of the Firefly Sparkle, progenitors of Milky Way-like galaxies were approximately 10,000 times less massive than today’s Milky Way. With the collaboration of observatories and surveys, researchers hope to uncover more lightweight galaxies akin to this one. Such discoveries could enhance our understanding of the early developmental phases of galaxies resembling our Milky Way.