Milky Way found larger than thought and may have flipped orientation after ancient collision

A new study using gamma‑ray bursts as high‑energy beacons mapped the farthest reaches of the Milky Way, showing the galaxy extends well beyond earlier estimates. The research, led by astronomer Beatrice Vaia, employed X‑ray and radio observations to chart outer regions previously hidden by dust.

Separate simulations conducted by Durham University astronomers, presented at the Royal Astronomical Society conference, suggest the Milky Way’s disk could have been tipped over after a massive merger with the dwarf galaxy Gaia‑Enceladus (also called the Sausage) roughly 10‑11 billion years ago. The Auriga cosmological simulation suite indicates this collision may have altered the galaxy’s orientation, changing the trajectories of billions of stars, possibly including the Sun.

Together, the findings reshape our understanding of the Milky Way’s size and dynamic history.