Pair of 'dancing' black holes in the galaxy

US astronomers have discovered the existence of two giant black holes moving like dancing around each other, in a distant galaxy.

Illustration of two black holes revolving around each other.Photo: P. Marenfeld, NOAO

Astronomers believe that most galaxies have a huge black hole in the central region. When two galaxies collide or merge, black holes in their centers can attract each other. Over time they will revolve around a double black hole formation and proceed to merge to become a larger black hole.

Astronomers have identified that the double black hole is relatively common in the universe, but we have no reliable evidence of their existence before. Meanwhile, Todd Boroson and Tod Lauer, two experts at the US National Optical Astronomical Station in Arizona, discovered two black holes during radiation analysis. "You can't see black holes, you just see their effects," Todd said.

With tremendous gravity, the two black holes move around each other in a place about 5 billion light-years from Earth (a light-year of 9.6 trillion km). The smaller black hole has a mass of 20 million times the sun, and the other black hole is 50 times smaller than a small black hole. Each black hole takes about 100 years to move all around the 'partner'.

'We found that the size of the galaxy and the mass of the black hole have a proportional relationship. When two non-homogeneous black holes in mass lie close together, it is likely that the larger galaxy has swallowed the small galaxy, ' Todd commented.