Astronomers Discover Rare Triple Black Hole System in Milky Way, Challenging Formation Theories

Astronomers have identified a black hole with a tightly bound companion star and a distant third star in orbit, forming the first-known “black hole triple” system. This discovery, detailed in recent research led by Kevin Burdge of the Massachusetts Institute of Technology (MIT), sheds new light on how some black holes may form more calmly than traditionally thought.

What Makes V404 Cygni Unique?

This rare system, called V404 Cygni, is around 8,000 light-years from Earth and lies within the Milky Way. It consists of a black hole and a nearby star, previously identified as an “X-ray binary,” where the black hole consumes material from its neighbouring star. However, new insights reveal that a third, much more distant star orbits this pair. This outer star completes a single orbit in an astounding 70,000 Earth years. This indicates a weak gravitational bond between the stars and the black hole.

A Surprising Birth Process

Ordinarily, black holes are born from violent supernova explosions, often imparting a “natal kick” to any loosely bound stars, ejecting them from the system. The presence of this third star in V404 Cygni suggests a different scenario. Researchers propose that this black hole might have formed through “direct collapse”. The direct collapse is a process where a star implodes quietly, sparing surrounding stars from a forceful kick.

Implications for Black Hole Research

This finding opens up questions about the formation of other black hole systems. “It’s intriguing to consider if there are more triple systems out there,” Burdge noted. These shows us how such arrangements could offer insights into black hole evolution. Observations from the Gaia space telescope confirmed the stars’ coordinated movements, with calculations suggesting there is only a one-in-10-million chance that these stars are not part of the same system.