In an astounding display of technical precision and pure unflagging tenacity, astrophysicists have detected a dark celestial dance. Two supermassive black holes are circling each other 750 million light years from the earth.
Their motion may tell us what happens when galaxies collide.
This is the first binary system of black holes ever witnessed by astronomers. It was made possible with the use of the Very Long Baseline Array (VLBA), a system of ten radio telescopes spread out from the Virgin Islands to Hawai'i. Controlled from Socorro, New Mexico, the VLBA uses patterns of electromagnetic interference, interferometry, to divine information from the distant heavens.
Interferometers have the most accurate length resolution of any scientific instrument, often detecting nanometer distances. A team of scientist recently turned the VLBA--which despite its unusual nature is best thought of as one telescope-on radio galaxy 0402+379. It noted motion changes, years of them.
Then, using advanced computer power that processed interference data, they came to the firm conclusion that two massive core objects are circling each other. They published their results in the Astrophysical Journal.
These objects are black holes, and supermassive ones that. The two of them together have a mass at least 15 billion times that of the sun. Without admitting light, these objects, which are about 24 light years apart, orbit each other once every 30,000 Earth years.
The data necessary to make the calculations took twelve years to collect. A supercomputer was necessary to crunch all the interferometry data.
How did it come about that this massive pair engaged in this astro-dance? Consider the Milky Way galaxy. At its center is a Sagittarius "A-Star" (written Sagittarius-A*, or Sgr-A*). This black hole is so massive that the rest of the galaxy rotates around it.
Most galaxies are structured like ours, but what happens when two typical galaxies collide with each other? Space is so warped around a black hole that if one galactic center came near another, the two would circle each other in a contest of the greatest space-warpers of the universe.
Astronomers have predicted galaxies would meet and their supermassive core black holes would interact. But the precise work of a team using the most precise measuring tool we have has determined the exact nature of this dance of Titans.
