In NGC 6240, a galaxy located 400 million light years from the Milky Way, two supermassive black holes are locked in a battle that will eventually end in a mammoth collision. In fact, the collision of two supermassive black holes is as energetic as it can get, generating powerful ripples through the fabric of space. The two supermassive black holes in NGC 6240 are expected to merge as one super-supermassive black hole once the dust has eventually settled.
The energetic ripples are known as gravitational waves and astrophysicists are spending a lot of time and money trying to detect them (although they've had little luck so far).
The two black holes in NGC 6240 are currently spinning around each other at a distance of only 3000 light years. But how did two supermassive black holes — both with the mass of millions of suns — get so close? After all, these gravitational monsters usually evolve in the center of galaxies, alone.
NGC 6240 is in fact two galaxies, that collided, and merged as one. The black holes from each of the galactic nuclei started to orbit around one another about 30 million years ago and they are expected to make contact in tens or hundreds of millions of years from now.
In this striking image, optical light (from the Hubble Space Telescope) and X-ray data (from the Chandra X-ray Observatory) have been combined, highlighting the two supermassive black holes as they stare at each other across the chaos of disturbed stars, dust and hot gas in the center of NGC 6240.