A rare black hole trio: Astronomers discover the first triple 'black hole system' in our own Milky Way

An illustration depicts the black hole in V404 Cygni drawing material from a companion star, while a more distant star in the system maintains a safer orbit. (Image: NASA)

Astronomers have revealed a remarkable cosmic discovery: the first known black hole triple system. This unique find, identified as V404 Cygni, is located 8,000 light-years away in our own Milky Way. In this trio, a black hole voraciously consumes its close companion star, while a distant star orbits more cautiously. This discovery hints at a gentler origin for black holes than previously thought.

A Gentle Giant? Black Hole Formation Without a Supernova

Typically, black holes emerge from the violent deaths of stars, with supernova explosions flinging nearby objects outward. However, V404 Cygni’s setup challenges this norm, suggesting a more “gentle” formation process known as "direct collapse." If V404 Cygni had experienced a dramatic supernova kick, it likely would have launched the outer star from the system.

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The research, led by Kevin Burdge from MIT, confirms V404 Cygni as a triple system — an extremely rare setup for a black hole. Burdge's team examined 10 years of data from the Gaia space telescope to verify that V404 Cygni’s third star genuinely shares this complex gravitational dance with the inner binary.

Burdge expressed his excitement over the find: "It’s thrilling because it changes our view on black hole formation." According to Burdge, this discovery proves that some black holes form without a powerful supernova kick, meaning they stay more connected with nearby stars.

V404 Cygni’s structure includes an “X-ray binary” — a system where the black hole actively consumes its victim star. This devouring cycle, which happens every 6.5 days, leaves behind X-ray signatures that scientists have monitored. Meanwhile, the third, more distant star takes an extraordinary 70,000 years to complete its orbit around the black hole.

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This triple arrangement might seem precarious, but the team’s simulations reveal a logical explanation. Burdge’s team ran thousands of scenarios with varying levels of supernova energy, simulating potential outcomes. Most simulations showed the outer star would be ejected unless the black hole formed by direct collapse.

V404 Cygni: A 4-Billion-Year-Old Cosmic Trio

The outer star’s current transformation into a red giant has allowed the team to estimate the system’s age. They’ve concluded that V404 Cygni is about 4 billion years old, the first time scientists have dated an old black hole with such accuracy.

The team’s next challenge is to study the outer star’s orbit. They aim to measure its shape — whether it’s circular or eccentric — with the GRAVITY instrument on the European Very Large Telescope. "This is the first known black hole triple," said Burdge, “but we’re determined to find more.”

Burdge’s team published their findings in Nature, marking a pivotal moment in black hole research. With this discovery, astronomers may have a clearer path to understanding these elusive cosmic giants and their formation mysteries.