"The surface of the Earth is the shore of the cosmic ocean... Recently, we've managed to wade a little way out, and the water seems inviting." - Carl Sagan
How do black holes get supermassive?
Since their discovery, supermassive black holes – the giants lurking in the center of every galaxy – have been mysterious in origin. Astronomers remain baffled as to how these supermassive black holes became so massive.
New research explains how a supermassive black hole might begin as a normal black hole, tens to hundreds of solar masses, and slowly accrete more matter, becoming more massive over time. The trick is in looking at a binary black hole system. When two galaxies collide the two supermassive black holes sink to the center of the merged galaxy and form a binary pair. The accretion disk surrounding the two black holes becomes misaligned with respect to the orbit of the binary pair. It tears and falls onto the black hole pair, allowing it to become more massive.
In a merging galaxy the gas flows are turbulent and chaotic. Because of this “any gas feeding the supermassive black hole binary is likely to have angular momentum that is uncorrelated with the binary orbit,” Dr. Chris Nixon, lead author on the paper, told Universe Today. “This makes any disc form at a random angle to the binary orbit.”
Image credit: Nixon et al.