Two galaxies, both alike in dignity — er, size — are in the midst of waging gravitational warfare upon one another, and they're really doing a number on each other in the process. Each galaxy is similar in size and shape to our own: they're spiral galaxies with super-massive black holes at their cores. And it's those black holes that started this whole business.
Like star-crossed lovers, the black holes have become attracted to one-another and are hell-bent on being together. No matter what that means for their celestial families.
Incidentally, what it means for their celestial families is a lot of crashing, exploding and heat. The cloud of gaseous debris that is the result of this galactic collision has been measured as spanning 300,000 light years. That's four times as far as Voyager was thrown in its namesake Star Trek series. Meaning that, even by Trek standards, it would take centuries to traverse. With current technology: fuggetaboutit.
The gas cloud also contains as much mass as 10 billion Suns. That's a lot of Suns — and a lot of mass. If that weren't impressive enough, the entire cloud seems to be radiating a temperature upwards of 7 million degrees. That's some hot intergalactic action right there. Scientists have only recently completed a composite image of the phenomenon, using visual data from the Hubble Space Telescope and thermal imaging from the Chandra X-Ray telescope, which is how we're able to bring you this stunning visual event that's been going on for about 20 million years.
For more information on the event itself, check out the Chandra Observatory's podcast here.