New images show galaxy forming that is similar in mass to young Milky Way

New images show a galaxy forming that is similar to what our Milky Way’s mass might have been at the same stage of development.

Nasa’s James Webb Space Telescope has detected and “weighed” a galaxy that existed about 600 million years after the Big Bang.

Other galaxies Webb has detected at this time period are significantly more massive, Nasa said.

Lamiya Mowla, co-lead author of the paper and an assistant professor at Wellesley College in Massachusetts, said: “I didn’t think it would be possible to resolve a galaxy that existed so early in the universe into so many distinct components, let alone find that its mass is similar to our own galaxy’s when it was in the process of forming.

“There is so much going on inside this tiny galaxy, including so many different phases of star formation.”

The research team modelled what the galaxy might have looked like if it were not stretched and discovered that it resembled an elongated raindrop. Suspended within it are two-star clusters toward the top and eight toward the bottom.

Kartheik Iyer, co-lead author and Nasa Hubble Fellow at Columbia University in New York, said this galaxy is “literally in the process of assembling”.

Webb’s data shows the Firefly Sparkle galaxy is on the smaller side, falling into the category of a low-mass galaxy. Billions of years will pass before it builds its full heft and a distinct shape.

Professor Mowla added: “Most of the other galaxies Webb has shown us aren’t magnified or stretched, and we are not able to see their ‘building blocks’ separately.

“With Firefly Sparkle, we are witnessing a galaxy being assembled brick by brick.”

Chris Willott from the National Research Council of Canada’s Herzberg Astronomy and Astrophysics Research Centre, a co-author and the observation program’s principal investigator, said: “This galaxy has a diverse population of star clusters, and it is remarkable that we can see them separately at such an early age of the universe.

“Each clump of stars is undergoing a different phase of formation or evolution.”

The galaxy’s projected shape shows that its stars have not settled into a central bulge or a thin, flattened disk, another piece of evidence that the galaxy is still forming, Nasa added.

Researchers cannot predict how this disorganised galaxy will build up and take shape over billions of years, but there are two galaxies that the team confirmed are “hanging out” within a tight perimeter and may influence how it builds mass over billions of years.

Firefly Sparkle is 6,500 light-years away from its first companion, and its second companion is separated by 42,000 light-years. The fully formed Milky Way is about 100,000 light-years across — all three would fit inside it.

Not only are its companions very close, but the researchers also think that they are orbiting one another.

Each time one galaxy passes another, gas condenses and cools, allowing new stars to form in clumps, adding to the galaxies’ masses.

Yoshihisa Asada, a co-author and doctoral student at Kyoto University in Japan, said: “It has long been predicted that galaxies in the early universe form through successive interactions and mergers with other tinier galaxies.

“We might be witnessing this process in action.”