The Hubble Space Telescope has uncovered evidence of a massive ancient galactic collision that predates the Milky Way’s known major crash by roughly 18億年. Researchers analyzing old globular clusters found a distinct chemical and chronological grouping dubbed Low-energy-Kraken-Heracles, revealing that a progenitor galaxy with a mass of about five hundred million solar masses merged with the early Milky Way roughly 距今約123億年前的宇宙早期.
The Gaia-Sausage-Enceladus Precedent
Reconstructing the growth of our galaxy resembles an exercise in deep-time archaeology. Astronomers have long understood that the Milky Way expanded not as a solitary monolith, but by continually cannibalizing smaller nearby dwarf systems. For years, the most violent chapter in this ongoing cosmic consumption was thought to be the Gaia-Sausage-Enceladus, or GSE, event. That collision occurred roughly 大約 105 億年前 when a massive system slammed into the nascent Milky Way.
Data from the European Space Agency’s Gaia satellite originally mapped the high-velocity halo stars that defined the GSE merger. Those stars trace out an elongated sausage-shaped velocity distribution. That collision tore the incoming galaxy apart and triggered massive bursts of star formation. Yet this newest study proves the GSE event was not the solitary feast once imagined by the scientific community.
Decoding Star Clusters With Hubble
The research team utilized precise observational data from the Hubble Space Telescope to examine the relative ages and chemical compositions of ancient globular clusters residing within the Milky Way. Researchers tracked the age-metallicity distribution of these clusters and sorted them into three distinct populations. The first group belongs to the native Milky Way, while the second group represents leftovers from the GSE crash. The third group represents a brand-new intermediate sequence.
Mapping the LKH Structure
That third sequence points directly to a merger occurring approximately 距今約123億年前的宇宙早期. The remnants of this ancient encounter, named the Low-energy-Kraken-Heracles or LKH structure, deposited most of its stellar material within twenty thousand light-years of the galactic center. The study mapping this ancient merger has been published in Nature Astronomy, according to Taipei Astronomical Museum reporting.
Rewriting the Milky Way Timeline
Pinpointing the precise ages of globular clusters acts as a primary tool for modern cosmic archaeology. The discovery of the LKH collision fills a critical gap in the early timeline of our galaxy’s youth. It demonstrates that galactic growth dynamics were far more frequent and violent than previously calculated. As instrumentation improves, space telescopes continue to push our horizon deeper into the universe’s formative epochs.
