Scientists Pinpoint Sagittarius A*’s Spin Speed Using X‑ray Clues
A team of astrophysicists from the United States and Canada has estimated how swiftly the Sagittarius A* black hole at the heart of the Milky Way is rotating. The study appeared in a prominent astronomy journal, helping scholars in North America and beyond better understand the dynamics of our galaxy’s central engine.
Researchers relied on data from the Chandra X‑ray Observatory, examining radio waves and other emissions from streams of matter swirling near Sagittarius A*. By tracing how material moves in the intense gravity well, scientists can infer how fast a black hole can spin.
To quantify rotation, a dimensionless parameter is used that ranges between 0 and 1. In this framework, 1 represents the theoretical maximum spin a black hole could achieve, given its mass and the amount of material it accretes. The speed of light sets a hard ceiling on spin, while the black hole’s size and feeding rate shape how close it can come to that limit.
The calculations indicate that Sagittarius A* is spinning with a value between 0.84 and 0.96, nudging toward the upper end of its possible range. This places the Milky Way’s central black hole among the fastest rotators known in the universe, a finding that carries significant implications for theories of black hole growth and behavior in galactic centers. (Citation: Monthly Notices of the Royal Astronomical Society)
Experts also suggest that a black hole’s spin can be influenced by its accretion disk, a ring of hot, infalling material shaped by the hole’s gravity. This mechanism could help explain how Sagittarius A* reached speeds comparable to the spin of the more massive black hole at the center of the M87 galaxy, even though M87’s black hole weighs about a thousand times more than Sagittarius A*.
Understanding the spin rate is not just an academic exercise. It informs how black holes form and evolve, how they interact with their surroundings, and how jets and winds might emerge from the disk‑bearing systems that orbit them. The new result adds a valuable data point to the broader map of black hole demographics across the cosmos, including in nearby galaxies in North America and beyond.
Earlier investigations leveraged the James Webb Space Telescope to scrutinize the Milky Way’s core with unprecedented detail. The newer evidence from X‑ray observations complements optical and infrared insights, offering a more complete picture of the dynamic environment near Sagittarius A* and how its rotation relates to the larger galactic center scenario.