Hubble Proves Milky Way Devoured A Massive Galaxy Billions Of Years Ago

by Aaron Leong — Tuesday, August 18, 2026, 10:56 AM EDT

Artist concept of LKH colliding with a young Milky Way — Artist concept of LKH (left) colliding with a young Milky Way (right) - Image: NASA, ESA, Joseph Olmsted (STScI)

Astronomers have uncovered concrete evidence of the earliest known galactic merger in the Milky Way's history, whereby our home galaxy devoured a dwarf galaxy nearly 12 billion years ago to fuel its initial growth spurts.

Detailed in a study led by astronomer Davide Massari, the discovery pushes back the known timeline of our galaxy’s major construction events by 1.8 billion years. By analyzing the orbits, ages, and chemical compositions of stellar clusters to reconstruct the primal catastrophe, Massari and his team concluded that this event occurred around 11.8 billion years ago, just two billion years after the Big Bang. The consumed entity, an ancient dwarf galaxy known to astronomers as Kraken (or Low-energy Kraken/Heracles), is likely one of the most substantial and influential mergers in Milky Way history.

The scientists estimate that at the time of the cataclysmic merger, LKH contained a stellar mass equivalent to roughly 500 million Suns, or about a quarter of the size of the infantile Milky Way. Rather than destroying the nascent Milky Way, the cosmic impact supplied a massive influx of stars, dark matter, and volatile interstellar gas.

To unravel this mystery, the researchers analyzed observations from NASA’s Hubble Space Telescope alongside data from the European Space Agency’s Gaia observatory. They probed dense globular star clusters nested deep within the innermost 20,000 light-years of the Milky Way. And because these ancient star clusters preserve their original chemical composition and orbital trajectories, they act as time capsules that preserve the unique fingerprint of the galaxy in which they were born.

The study also notes that while the stars themselves drifted peacefully into the Milky Way's growing stellar halo without individual collisions, the gas clouds collided with explosive intensity. The shockwaves triggered widespread, rapid bursts of new star formation across the expanding galaxy.

However, the Milky Way v LKH battle isn't the only time our galaxy cannibalized another cosmic object. Between 8 to 11 billion years ago, the Milky Way absorbed another major dwarf galaxy, Gaia-Sausage-Enceladus (GSE), and actually continues to devour the smaller Sagittarius dwarf galaxy today. Another future merger is in the cards, including a predicted meeting with our neighboring Andromeda galaxy roughly 4.5 billion years from now.