When Galaxies Collide

About this episode

This episode explores the dynamic interactions of galaxies, including collisions and mergers, while featuring insights from astrophysicist Enrique López Rodríguez.

This week we continue our month-long journey through the world of galaxies, but this time, we move beyond what galaxies are and explore what galaxies actually do. It turns out these vast islands of stars are anything but static. They collide, merge, exchange gas and dust, fling stars into deep space, and sometimes grow by consuming smaller neighbors in a process astronomers call galactic cannibalism. We begin close to home with the Sagittarius Dwarf Spheroidal Galaxy, a hidden companion galaxy currently being torn apart by the gravity of our own Milky Way. From there, we travel some 70 million light-years away to the spectacular Antennae Galaxies, where two spiral galaxies are locked in a slow-motion collision that is both destructive, and strangely creative. Along the way, we recall my recent conversation with astrophysicist Enrique López Rodríguez to explore the possibility of magnetic bridges and “superhighways” carrying gas, dust, and charged particles between galaxies, raising the astonishing possibility that the raw ingredients of future planets may sometimes originate far beyond their home galaxy. And finally, we return to the question we teased last week: What about us…

People in this episode

Guest: Enrique López Rodríguez

Topics covered

• galaxy collisions
• galactic cannibalism
• Antennae Galaxies
• Sagittarius Dwarf Spheroidal Galaxy
• Milky Way
• Andromeda Galaxy
• night sky

Keywords

• galaxies
• collisions
• mergers
• gas exchange
• stellar dynamics
• Milky Way
• Andromeda
• Antennae Galaxies
• Hubble
• Gaia

Mentioned in this episode

Organizations: Hubble Space Telescope, Gaia

Places: Milky Way, Sagittarius Dwarf Spheroidal Galaxy, Antennae Galaxies, Andromeda Galaxy

More episodes of Star Trails: A Weekly Astronomy Podcast

• A Summer Sky Road Trip · June 7, 2026 · 31 min
• From the Archive: Star Party Stories · May 31, 2026 · 18 min
• The Birth and Death of Galaxies · May 24, 2026 · 29 min
• The Hidden Universe: Cosmic Structures in the Dark · May 17, 2026 · 22 min
• Where the Milky Way Begins… and Ends · May 3, 2026 · 23 min
• The Invisible Architecture of the Universe, with Dr. Enrique Lopez Rodriguez · April 26, 2026 · 38 min