The Gravity Tango

2 October 2014

A composite image of the galaxy cluster Abell 400. X-ray: NASA/CXC/AIfA/D.Hudson & T.Reiprich et al.; Radio: NRAO/VLA/NRL
A composite image of the galaxy cluster Abell 400.

The image above shows two supermassive black holes orbiting each other. It is a composite image where the blue/white indicates x-rays and the pink indicates radio wavelengths. It may look like they are orbiting closely, but the black holes are about 25,000 light years apart, which is about the same distance the Sun is from the center of the Milky Way.

What’s particularly striking about this image is just how clearly we can see the features of this binary system. The hot accretion regions surrounding the black holes clearly show their locations, and each black hole shows jets in radio. It’s not often that we can see a supermassive black hole with such detail.

These two black holes are in the process of merging. Within millions of years they will eventually coalesce into a single supermassive black hole. We aren’t sure just how long that will take because we don’t know the exact masses of these black holes.

Such black hole mergers are relativity common on a cosmic scale. In about 4 billion years our own Milky Way will collide with the Andromeda galaxy, and over time the supermassive black hole in our galaxy with merge with Andromeda’s supermassive black hole.

So in a way this image hints at our future, when we shall do the gravity tango.