The First Observed Black Hole is 50% Larger than Previous Thought, and Spins Faster Than Any Others

Cygnus X-1’s black hole feeds on a companion star 40 times the Sun’s mass.

Key Takeaways

• The Cygnus X-1 black hole, spinning near the speed of light, is the fastest ever observed.
• New measurements show the black hole is 50% heavier than thought, at 21 solar masses.
• Its rapid spin challenges existing theories about how massive stars shed material over time.
• Parallax methods revealed Cygnus X-1 is 7,200 light-years away, farther than prior estimates.
• Cutting-edge telescopes continue to unveil surprising details about well-known cosmic objects.

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The Fastest Spinning Black Hole Ever Observed

Six decades after its discovery, Cygnus X-1, the first black hole ever detected, remains a puzzle for astronomers. Recent observations reveal it spins faster than any black hole ever recorded, nearing the speed of light. Additionally, new data show it is 21 times the mass of the Sun, making it 50% heavier than previously estimated and the most massive stellar-mass black hole directly observed.

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The black hole’s massive size and high rotational speed have led scientists to revisit theories about the life cycles of bright stars that form black holes. Stellar winds typically strip such stars of their mass as they evolve, but Cygnus X-1 challenges this norm. Researchers suggest it may have lost less mass over its lifetime than models predict, allowing it to retain its extraordinary heft and spin.

Distance, Mass, and Advanced Observations

To refine the measurements of Cygnus X-1, astronomers used parallax—a technique that calculates stellar distances based on their apparent motion against the backdrop of distant stars as Earth orbits the Sun. Using the Very Long Baseline Array (VLBA), a network of 10 radio telescopes across the United States, researchers tracked the system’s full orbit over six days. They determined that the black hole lies about 7,200 light-years from Earth, significantly farther than the previous estimate of 6,000 light-years.

The black hole Cygnus X-1 is pulling material from a massive blue companion star. That “stuff” forms an accretion disk around the black hole. (Image credit: NASA/CXC)

This updated distance means its blue supergiant companion star is also more massive and brighter than expected, with a mass 40 times that of the Sun. Combined with the black hole’s orbital period, these findings provided the recalculated mass of Cygnus X-1’s black hole.

Cygnus X-1 also produces distinct emissions as it devours material from its companion star. The process forms a glowing disk of matter around the black hole, heating it to millions of degrees and generating intense X-ray radiation. Jets of material escaping this process emit radio waves detectable from Earth, which played a key role in the recent observations.

Implications and the Future of Astronomy

These discoveries highlight the importance of technological advancements in astronomy. Improved telescope sensitivity and precision have allowed scientists to refine their understanding of even well-studied celestial phenomena. The findings challenge assumptions about how stars evolve into black holes, particularly the role of metallicity and mass loss through stellar winds.

Astronomers are optimistic about future breakthroughs as next-generation telescopes come online. These tools promise to uncover even more mysteries about black holes and other cosmic phenomena. “It’s a great time to be an astronomer,” said Xueshan Zhao, a researcher at the National Astronomical Observatories of the Chinese Academy of Sciences.