Our most massive satellite galaxy, the Large Magellanic Cloud (LMC), has been the center of a heated debate in the astrophysics community over the last few years. That debate centers on whether this is the LMC’s first or second “pass” by the Milky Way itself — and it has huge implications for the evolution of our galaxy given the disruption such a large grouping of stars has. A new paper from Scott Lucchini, Jiwon Jesse Han, Sapna Mishra, and Andrew J. Fox and his co-authors, currently available in pre-print on arXiv, provides what they claim to be definitive evidence that this is, in fact, the first time LMC has encountered the Milky Way.

To understand the debate, it’s best to look at its history. For decades, there was an ongoing debate about the orbital path of the LMC. The discussion centered around a collisionless N-body dynamics model that tracked stars and their gravity. But back in 2024, physicist Eugene Vasiliev released a stunning paper that presented an argument that the LMC might have first passed the Milky Way 6–8 billion years ago at a distance of roughly 100 kiloparsecs.

Upon release of that paper, the debate was reignited. Vasiliev posited that, if the Milky Way’s dark energy halo was anisotropic (meaning the velocities of dark matter particles are skewed in certain directions), the current speed and position of the LMC would align perfectly with a “second pass” orbit. Dr. Lucchini and his co-authors are firmly on the other side of that argument.