Nasa's James Webb Space Telescope has spotted a young galaxy dating to the early universe – called Firefly Sparkle because its gleaming star clusters resemble the bioluminescent bugs – in a discovery that is giving astronomers a peek at what our Milky Way may have looked like in its infancy.

Researchers said the galaxy, still in the process of assembling, dates to when the universe was roughly 5 percent of its current age, about 600 million years after the Big Bang event that initiated the cosmos. It has a mass equal to about 10 million stars the size of our sun, and has two other relatively small galaxies as neighbours, dubbed Firefly-Best Friend and Firefly-New Best Friend.

It is comprised of 10 densely packed star clusters embedded in a diffuse arc of stars, eight in its central region and two along its extended arm. Its main visible portion spans about 1,000 light-years across. A light year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km).

The galaxy is estimated to have formed 100-400 million years before its evolutionary stage that was observed by Webb, the most capable space telescope ever deployed.

"The Milky Way began forming very early in the universe's history, likely around the same time as Firefly Sparkle," said astronomer Lamiya Mowla of Wellesley College in Massachusetts and the Centre for Astronomy, Space Science and Astrophysics in Bangladesh, co-lead author of the study published on Wednesday in the journal Nature. (Reuters)