Astronomy

Once thought to be unusual and rare, gravitational interactions between galaxies are now known to be quite common (especially in densely populated galaxy clusters) and are considered to play an important role in galaxy evolution. Here we can see two nearly identical spiral galaxies in Virgo, 90 million light-years distant, in the early stages of a gentle gravitational embrace. Like two skaters grabbing hands while passing, NGC 5427 (the nearly open-faced spiral galaxy at lower left) and its southern twin NGC 5426 (the more oblique galaxy at upper right), are in the throes of a slow but disturbing interaction-one that could take a hundred million years to complete.

At a glance, these twin galaxies-which have similar masses, structures, and shapes and are together known as Arp 271-appear undisturbed. But recent studies have shown that the mutual pull of gravity has already begun to alter and distort their visible features. Typically, the first sign of a galaxy interaction is the formation of a bridge-like feature. Indeed, the two spiral arms on the western (upper) side of NGC 5426 appear as long appendages that connect with NGC 5427. This intergalactic bridge acts like a feeding tube, allowing the twins to share gas and dust with one other across the 60,000 light years (less than one galaxy diameter) of space separating them.

This image was obtained at the Gemini South telescope in Chile using GMOS, the Gemini Multi-Object Spectrograph. (Picture credits: Gemini Observatory)

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