Interacting Galaxies Gallery

Thanks to the era of space-based telescopes, we no longer perceive galaxies as lonely islands of stars hanging in the deep void of space, but see them instead as dynamic and sprawling metropolises that interact with their neighbours, either gently nudging past each other in a cosmic tango or suffering cataclysmic smash-ups, spawning new and even more intricate shapes.

The main stages of galactic interaction. See text below for details. Image: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University), K. Noll (STScI), and J. Westphal (Caltech).

The first tentative sign of a galactic interaction is a bridge of matter as the gentle tugs of gravity tease out dust and gas from an approaching galaxy (frame 1). As the outer reaches of the galaxy impinges upon another, long streamers of gas and dust stretch out and sweep around the galaxy cores (frame 2). These long ‘tidal tails’ can persist long after the main action is over (frame 3). Once the galaxy cores begin to interact, their gas and dust clouds are buffeted and pulled in all directions, resulting in shock waves that rip through the interstellar clouds (frame 4). Furious star burst formation is triggered as gas and dust are siphoned into the active central regions (frame 5). Some of the galaxies show highly distorted features, with dust lanes crossing between the galaxies and long filaments of stars extending far beyond the central regions (frame 6). Even apparently isolated galaxies can bear the scars of a previous merger event.

In anticipation of the upcoming Hubble repair mission following its 18th anniversary in space this year, we present 18 choice images capturing the weird and wonderful world of galactic interactions that may ultimately define the fate of our own Milky Way (see the October issue of Astronomy Now for more!). Click each image for enlarged version and caption.

All images: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration

For a look five billion years into the future to discover the destiny of the Milky Way as it hurtles towards the Andromeda Galaxy, get your hands on a copy of the October issue of Astronomy Now magazine, available to buy from 18 September.