Hubble Just Opened a Brighter First Chapter of the Milky Way’s Story

A bright river of stars can feel wonderfully familiar when you look up at the Milky Way, but this week astronomers made that familiar band feel new again. Using Hubble data, they found strong evidence that one of the first big building steps in our home galaxy came from a long-ago collision with a smaller dwarf galaxy called Low-energy-Kraken-Heracles, or LKH, around 11.8 billion years ago [ref:1][ref:3].

The delightful part of this story is how it was solved. Researchers did not watch two galaxies crash in real time. Instead, they read the Milky Way’s oldest keepsakes: globular clusters, those densely packed star swarms that can hold tens of thousands to a few million stars each [ref:1]. By measuring the ages and metal content of clusters deep in the galaxy, the team turned Hubble into a kind of cosmic archivist [ref:1][ref:3].

A new first chapter for our galaxy

The paper was published in Nature Astronomy on 17 August 2026, and it pushes the Milky Way’s documented merger history 1.8 billion years farther back than before [ref:1][ref:3]. Until now, one of the best-known early milestones was the Gaia-Sausage-Enceladus merger about 10 billion years ago, while the Sagittarius dwarf merger began more than 6 billion years ago and is still unfolding today [ref:1][ref:3].

What Hubble added was a deeper chapter. The team found evidence for an earlier merger that happened just 2 billion years after the Big Bang, when the Milky Way itself was still young and much smaller [ref:1][ref:2]. That makes this result feel less like a footnote and more like a foundation stone.

How astronomers read ancient star clusters

Researchers analyzed 39 globular clusters in the inner 20,000 light-years of the Milky Way, exactly where traces of the oldest mergers were most likely to survive [ref:1]. Globular clusters are useful because they preserve old stellar populations with unusual fidelity. Think of them as sealed boxes from the galaxy’s childhood.

The team expected to see two familiar families in the data: clusters born inside the young Milky Way, and clusters that arrived with Gaia-Sausage-Enceladus about 10 billion years ago [ref:1][ref:2]. Instead, Hubble’s precise age measurements and Gaia’s supporting data revealed a third sequence — older than the Gaia-Sausage-Enceladus group, but younger than the Milky Way’s original in-house clusters [ref:1][ref:2].

That third sequence is the key clue. In the Nature paper, the newly identified merger deposited most of its mass in the inner 6 kiloparsecs of the Milky Way, and the progenitor appears to have carried about 5 × 10^8 solar masses in stars — roughly 500 million Suns’ worth of stellar material [ref:3]. That is large enough to matter profoundly in the architecture of a young galaxy.

Why LKH matters

Astronomers named the lost dwarf galaxy Low-energy-Kraken-Heracles, or LKH, partly in tribute to earlier papers that predicted such an event [ref:1][ref:3]. The name sounds mythic, but the science is refreshingly concrete: a third age-metallicity sequence, a distinct group of inner-halo clusters, and a merger date around 11.8 billion years ago [ref:2][ref:3].

The finding also sharpens a bigger idea. Some earlier studies suggested the Milky Way’s very first stages were shaped mainly by stars born inside the galaxy itself. Lead author Davide Massari said this work shows stars from outside galaxies also need to be counted in that earliest history [ref:1][ref:2]. In other words, our galaxy grew through welcome additions much earlier than many astronomers could prove before.

A happier kind of cosmic archaeology

One reason this result feels so appealing is that it makes the universe look wonderfully legible. Hubble has been operating for more than three decades, and here it is still helping astronomers recover a story written nearly 12 billion years ago [ref:1]. The clues were not flashy explosions or giant headlines in the sky. They were quiet differences in the ages and chemistry of ancient star clusters.

That is a lovely lesson to carry into your next look upward. The Milky Way is not only a glowing band across the night. It is a layered family album. And thanks to 39 carefully studied globular clusters, one of its earliest missing pages has just been placed back where it belongs [ref:1][ref:3].