How to weigh a ghost: measuring the universe's most distant dormant giant
In short: Black holes are often thought of as active, light-devouring monsters. But most are actually 'dormant'—practically invisible because they aren't currently feeding on gas. Scientists have just achieved a breakthrough by weighing one of these cosmic ghosts at a record-breaking distance, using nothing but the motion of nearby stars.
While active galactic nuclei (AGN) glow brightly as they consume matter, dormant black holes are far more elusive. Because they lack a steady supply of gas to create radiation, they are nearly impossible to see directly. To overcome this, astronomers use a technique called stellar dynamics. By observing how stars orbit a central point, researchers can infer the mass of the invisible object exerting the gravitational pull. This same method was used to weigh Sagittarius A*, the 4.3-million-solar-mass black hole at the center of our own Milky Way, which sits only 26,000 light-years away.
The latest breakthrough involves the galaxy MRG-M0138, located over 10 billion light-years away. Using the James Webb Space Telescope (JWST) and Einstein's theory of gravitational lensing, an international team measured a dormant supermassive black hole at its heart. This object weighs approximately 6 billion times the mass of the sun. Captured during a period when the cosmos was merely 3 billion years old—approximately one-fourth of its present age—this data offers a unique view of the nascent universe.
This discovery is significant because it represents a massive leap in observational range. The previous record for weighing a dormant black hole using stellar dynamics was a galaxy just 700 million light-years away. The new measurement is about 15 times farther than that previous record. By proving this technique works at such cosmological distances, scientists can begin a more complete census of how black holes develop and how they shape the evolution of galaxies over billions of years.
The study of these objects also touches on the long history of black hole verification. In 1975, physicists Stephen Hawking and Kip Thorne famously engaged in a wager over Cygnus X-1. While Hawking initially bet it wasn't a black hole, the intense study of such entities eventually confirmed their existence as real celestial objects capable of warping both space and time.
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Sources
- Summary by Intellect · source: Dormant Black Hole Found Near the Solar System and It's Huge
- Also: James Webb Space Telescope weighs
- Also: Researchers weigh the most distant dormant black hole
- Also: JWST 'weighs' dormant black hole 10 billion light-years away
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