LKH Milky Way merger (artist’s impression)

About 12 billion years ago, a dwarf galaxy known as LKH (left) collided with a young Milky Way (right) and merged with it. This artist’s concept portrays that collision. The NASA/ESA Hubble Space Telescope uncovered definitive evidence of this long-ago collision by studying ancient globular star clusters.

[Image description: An illustration of two galaxies in the midst of a collision against a dark, star-filled background. The collision takes up the middle third of the illustration. On the right, a larger galaxy is viewed at an angle from 11 o’clock to 4 o’clock, with a white-yellow core surrounded by mottled brown dust lanes and faint bluish spiral arms. To the left, a smaller, bright blue-white galaxy is stretched into a curved, hook-like shape as gravity distorts it. A broad, glowing bridge of pale blue gas and stars extends off the galaxy at the left, while wispy streams extend above and below the larger galaxy at the right. The words “Artist’s Concept” appear in the lower left corner.]