Almost every galaxy in the universe has a supermassive black hole at its core, weighing anything between a few million and billions of times the mass of the Sun. How these objects form is still a mystery, but according to a new simulation we might be able to find out in the coming decades.
Presented at the National Astronomy Meeting in Nottingham, researchers from Durham University used realistic simulations of the universe to estimate that at least one gravitational wave signal from a supermassive black hole will be detectable every year once eLISA – ESA's upcoming gravitational wave space observatory – is launched in 2034.
In the universe today, we "see" two types of black holes: stellar black holes formed in the largest supernovae, and supermassive black holes found in the center of galaxies. These supermassive black holes are believed to have formed from the repeated mergers of smaller black holes, and their evolution is closely linked to the evolution of galaxies.
“Black holes are fundamental to galaxy formation and are thought to sit at the center of most galaxies, including our very own Milky Way,” Professor Richard Bower, co-author of the study, said in a statement. “Discovering how they came to be where they are is one of the unsolved problems of cosmology and astronomy. Our research has shown how space-based detectors will provide new insights into the nature of supermassive black holes.”
Compared ground-based detectors like LIGO, which discovered gravitational waves this year, eLISA will be 250,000 times larger. The precursor mission, LISA Pathfinder, has just successfully demonstrated the necessary technology for eLISA.
Although LIGO was able to detect the gravitational waves from small black holes, it is not capable of detecting the waves from supermassive black holes as they have a much lower frequency. eLISA will be able to detect these collisions, and the researchers are confident that the shape of the signal will strongly depend on the original colliding object.
“Understanding more about gravitational waves means that we can study the universe in an entirely different way,” said lead author Jaime Salcido. “By combining the detection of gravitational waves with simulations, we could ultimately work out when and how the first seeds of supermassive black holes formed.”
It might seem premature to prepare such detailed analysis years before it will be needed, but accurate theoretical predictions are paramount to successful science and it’s never too early to start.