Tale of a doomed galaxy (part 1)
About 3 billion years ago, if there was intelligent life on the galaxy we call PG 1302-102
, it should have known it was doomed.
Our galaxy has a supermassive black hole in the middle. But that galaxy had two
. One was about ten times as big as the other. Taken together, they weighed a billion times as much as our Sun.
They gradually spiraled in towards each other... and then, suddenly, one fine morning, they collided. The resulting explosion was 10 million times more powerful than a supernova - more powerful than anything astronomers here on Earth have ever seen! It was probably enough to wipe out all life in that galaxy.
We haven't actually seen this yet. The light and gravitational waves from the disaster are still speeding towards us. They should reach us in roughly 100,000 years. We're not sure when.
Right now, we see the smaller black hole still orbiting the big one, once every 5 years. In fact it's orbiting once every 4 years! But thanks to the expansion of the universe, PG 1302-102 is moving away from us so fast that time on that distant galaxy looks significantly slowed down to us.
Orbiting once every 4 years: that doesn't sound so fast. But the smaller black hole is about 2000 times more distant from its more massive companion than Pluto is from our Sun! So in fact it's moving at very high speed - about 1% of the speed of light. We can actually see it getting redshifted and then blueshifted as it zips around. And it will continue to speed up as it spirals in.
What exactly will happen when these black holes collide? It's too bad we won't live to see it. We're far enough that it will be perfectly safe to watch from here! But the human race knows enough about physics to say quite a lot about what it will be like. And we've built some amazing machines to detect the gravitational waves created by collisions like this - so as time goes on, we'll know even more.
I'll talk a bit more about these things in the days to come....
For now, try this:
• Ravi Mandalia, Black hole binary entangled by gravity progressing towards deadly merge, http://www.techienews.co.uk/9741247/two-candidate-black-holes-entangled-by-gravity-in-a-deadly-spiral/