Astronomers have spotted what appear to be two super massive black holes at the heart of a remote galaxy, circling each other like dance partners.
"At first we thought this galaxy's unusual properties might mean it was forming new stars at a furious rate," said Peter Eisenhardt, at NASA, "but on closer inspection, it looks more like the death spiral of merging giant black holes."
Follow-up observations revealed unusual features in the galaxy, including a lumpy tail of matter, or jet, thought to be the result of one black hole causing the jet of the other to sway.
"We think the jet of one black hole is being wiggled by the other, like a dance with ribbons," said Chao-Wei Tsai, "If so, it is likely the two black holes are fairly close and gravitationally entwined."
The findings could teach astronomers more about how super massive black holes grow by merging with each other.
Almost every large galaxy is thought to harbour a super massive black hole filled with the equivalent in mass of up to billions of suns.