Some astronomers believe that once two supermassive black holes get shut enough together, decreasing their distance to 1 parsec (3.2 light-years), they may dance for eternity.
An worldwide team of astronomers using NASA's Hubble Space Telescope found a thin disk whirling around a supermassive black hole 130 million light-years away, but the disk shouldn't exist there based on current theories.
On the other hand, this is important because the existence of these black holes alone could help astronomers to better understand the black holes.
"If the gravitational wave background is not detected this could indicate that supermassive black holes merge only over extremely long timescales, remaining as close separation binaries for many Hubble times, the so-called 'final-parsec problem, '" write the researchers. When material gets too close it's swallowed up, but in less active galaxies the black holes at their core don't have the gravitational might to continuously draw material from the surrounding galaxy. When galaxies merge, the supermassive black holes drift to the center of the newly unified galaxy and begin orbiting one another.
But that's where this discovery and gravitational waves come into things.
"This is an intriguing peek at a disc very close to a black hole, so close that the velocities and the intensity of the gravitational pull are affecting how we see the photons of light", explains Bianchi.
She continued and said, "For everyone in black hole physics, observationally this is a long-standing puzzle that we need to solve". However, researchers are now unclear as to the time it takes for black holes to merge - or indeed, if they merge at all.
Detecting the gravitational wave background using one of these pulsar timing arrays takes patience and plenty of monitored stars.
The telltale gravitational waves generated by merging supermassive black holes are outside the frequencies now observable by experiments such as LIGO and Virgo, which have detected the mergers of much smaller black holes and neutron stars. If a passing gravitational wave stretches or compresses the space between Earth and the pulsar, the rhythm is slightly thrown off. The louder the background noise, the bigger the timing disruption and the sooner the first detection will be made.
The Hubble Space Telescope, which is operated by NASA and the ESA, is fantastic for spotting objects residing in the distant reaches of space.
Goulding said, "Although supermassive black holes aren't directly visible through an optical telescope like Hubble, they are surrounded by bright clumps of luminous stars and hot gas drawn in by the powerful gravitational tug".