Scientists Find Smoking Gun of Ancient Galaxy Collision

According to research published using the Hubble Space Telescope, the Milky Way galaxy consumed a previously unknown dwarf galaxy named Low-energy-Kraken-Heracles approximately 11.8 billion years ago. Lead author Davide Massari of the Astrophysics and Space Science Observatory of Bologna and his team found that the early merger added stars with a mass equivalent to 500 million Suns, proving that external galactic building blocks shaped the cosmic home from the beginning.

Discovering the Low-energy-Kraken-Heracles Merger with Hubble

Over 13.6 billion years of cosmic evolution, stellar motions perturbed and erased the obvious shapes of devoured galaxies. To uncover the ancient event, Davide Massari and his research team used the Hubble Space Telescope to examine 39 different globular clusters. These densely packed groups contain up to millions of ancient stars held together by gravity. By measuring the precise age and chemical fingerprints, known as metallicity, of these ancient objects, researchers sorted the clusters into distinct populations.

Comparing Milky Way Galactic Meals Across Billions of Years

The Low-energy-Kraken-Heracles event stands as just one major meal in a long history of galactic cannibalism. Astronomers have mapped several distinct mergers that built the Milky Way over time. Ten billion years ago, the galaxy consumed the Gaia-Sausage-Enceladus dwarf galaxy, which significantly affected the structure of the stellar disk. Later, about 6 billion years ago, the Milky Way began swallowing the Sagittarius dwarf galaxy in a merger that remains ongoing today.

Why Ancient Mergers Change the Story of Our Galaxy

Astronomers long debated whether the infant Milky Way developed as a quiet, self-contained system where stars formed purely from internal gas clouds. The identification of the third cluster population—older than Gaia-Sausage-Enceladus but younger than native Milky Way clusters—demonstrates that external forces played an active role from the start. “Our home is the Milky Way galaxy, but we do not know how our house was built,” Massari states regarding the origins of the first significant batch of bricks.

Frequently Asked Questions

What is the Low-energy-Kraken-Heracles galaxy?

Low-energy-Kraken-Heracles, or LKH, is a newly discovered dwarf galaxy that was swallowed by the Milky Way approximately 11.8 billion years ago, adding a mass 500 million times that of the Sun.

How do astronomers detect ancient galaxy mergers?

Researchers use the Hubble Space Telescope to measure the precise ages and chemical fingerprints of ancient globular clusters, sorting them into populations to reveal distinct galactic origins.

Is the Milky Way still consuming other galaxies today?

Yes, astronomers note that the Milky Way is still actively swallowing the Sagittarius dwarf galaxy, a process that began about 6 billion years ago.