Data from the James Webb Space Telescope have provided a glimpse of our galaxy in its formative years. Webb observed a galaxy called The Sparkler, which is what the Milky Way would have looked like when it was young, when it was less massive and only a handful of globular clusters.
Our galaxy is one of the oldest in the universe, being around 13.8 billion years old. Over the course of its life, the Milky Way has grown with more and more stars until it has reached its current mass of about 1.5 trillion times the mass of the Sun. It also now hosts around 200 globular clusters, which are dense star clusters.
In contrast, the Sparkler galaxy has only 3% the mass of the Milky Way and only 24 globular clusters. But this small galaxy is growing as it engulfs nearby companion galaxies and globular clusters, and is predicted to eventually grow to the mass of the Milky Way.
“We appear to be witnessing firsthand this galaxy’s clustering as it builds its mass — in the form of a dwarf galaxy and several globular clusters,” lead author Duncan Forbes, of Australia’s Swinburne University, said in a statement. “We are excited about this unique opportunity to study both the formation of globular clusters and a young Milky Way at a time when the Universe was only 1/3 its current age.”
The Sparkler Galaxy is extremely distant, so it takes billions of years for its light to reach us. Researchers were able to get a better look at it using a technique called gravitational lensing, which means they see it as it was about 9 billion years ago.
This ability to see a galaxy growing just 4 billion years after the Big Bang can help us understand the formation of globular clusters, according to co-author Aaron Romanowsky: “The origin of globular clusters is a long-standing mystery, and we’re excited that JWST can look back in time to see them in their youth.”
The research results are published in the Monthly Notices of the Royal Astronomical Society.