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Astronomers have found an answer to a long-running mystery in astrophysics: Why are supermassive black holes today growing slower than in the past? A team of researchers used NASA’s Chandra X-ray Observatory and other X-ray telescopes to determine that supermassive black holes are unable to consume material as rapidly as they did billions of years ago during a period known as “cosmic noon.”
Why it matters
Understanding the growth patterns of supermassive black holes over cosmic time provides key insights into the evolution of galaxies and the universe as a whole. The slowdown in black hole growth has been a longstanding puzzle, and this new research helps explain the underlying causes.
The details
The researchers used X-ray data to track the growth of supermassive black holes at different distances from Earth, representing different time periods in the history of the universe. They found that while black hole growth was at its peak around 10 billion years ago during “cosmic noon,” it has since slowed down significantly. The team was able to disentangle the effects of black hole mass and growth rate on X-ray brightness to determine that the primary driver of the slowdown is a lack of available material for the black holes to consume.
Around 10 billion years ago was a period astronomers call “cosmic noon” when supermassive black hole growth was at its peak.Between cosmic noon and the present day, astronomers have observed a major slowdown in how much supermassive black holes are growing.
The players
Zhibo Yu
A graduate student in astronomy and astrophysics at the Eberly College of Science at Penn State and lead author of the study.
NASA’s Chandra X-ray Observatory
An X-ray telescope used by the researchers to track the growth of supermassive black holes over cosmic time.
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What they’re saying
“A longstanding mystery has been the cause of this big slowdown. With these X-ray data and supporting observations at other wavelengths, we can test different ideas and narrow down the answer.”
— Zhibo Yu, Graduate student in astronomy and astrophysics
The takeaway
This research provides important insights into the evolution of supermassive black holes and the broader development of galaxies and the universe over cosmic time. Understanding the factors driving the slowdown in black hole growth, such as the availability of consumable material, is a key step toward a more complete picture of these extreme cosmic phenomena.