A mysterious ‘dance’ where two enormous black holes, each with a mass millions or billions that of our sun, circle each other before one "eats" the other has been captured by a NASA space telescope.
The final stage of what NASA describes as “galactic cannibalism” is predicted to send mysterious gravitational waves rippling through space and time.
Enormous jets of mass and energy are spurting from the black holes, with one described as “lumpy” - and the image, captured by NASA's Wide-field Infrared Survey Explorer, or WISE space telescope, is described as a “death spiral”.
The image, NASA says, is “incredibly rare”, something that scientists have sought for years - and the cosmic duo’s fatal embrace could help us understand how the first galaxies formed.
Gravity waves were predicted by Einstein, but have never been detected - NASA hopes to detect the “ripples” of black holes merging by watching dead stars called pulsars, which emit radio pulses, “as regularly as atomic clocks”.
A tiny change as “ripples” in space time passed through them would prove Einstein right.
Supermassive black holes lurk at the centre of most galaxies - including our own. Black holes cannot be seen directly, as their gravity is so intense, even light cannot escape.
The Milky Way’s black hole, Sagittarius A*, is orbited by a swarm of stars whose paths let us measure the black hole’s mass: four million times the mass of the Sun.
Supermassive black holes are thought to form at the same time as the galaxy around them.
The duo was also observed the Australian Telescope Compact Array near Narrabri, Australia, and the Gemini South telescope in Chile - showing that the “double-yolked” galaxy is wiggling, as the two black holes dance closer and closer.
"We think the jet of one black hole is being wiggled by the other, like a dance with ribbons," said Chao-Wei Tsai of NASA's Jet Propulsion Laboratory, Pasadena, Calif., who is lead author of a paper on the findings appearing in the Dec. 10 issue of Astrophysical Journal. "If so, it is likely the two black holes are fairly close and gravitationally entwined."
The findings could teach astronomers more about how supermassive black holes grow to form the heart of galaxies. Some “grow” by consuming nearby stars and planets - but this observation, 3.8 billion light years from Earth, could be our first chance to understand what happens when galaxies collide.
"At first we thought this galaxy's unusual properties seen by WISE might mean it was forming new stars at a furious rate," said Peter Eisenhardt, at NASA’s Jet Propulsion Laboratory.. "But on closer inspection, it looks more like the death spiral of merging giant black holes."
When galaxies collide, their massive black holes sink to the center of the new structure, becoming locked in a gravitational tango. Eventually, they merge into one even-more-massive black hole.
The dance of these black hole duos starts out slowly, with the objects circling each other at a distance of about a few thousand light-years.
So far, only a few handfuls of supermassive black holes have been conclusively identified in this early phase of merging. As the black holes continue to spiral in toward each other, they get closer, separated by just a few light-years.
Daniel Stern of NASA’s JPL, said:. "There are several extremely unusual properties to this system, from the multiple radio jets to the Gemini data, which indicate a highly perturbed disk of accreting material around the black hole, or holes. Two merging black holes, which should be a common event in the universe, would appear to be simplest explanation to explain all the current observations."