Astronomers have detected an ultra-fast wind from the supermassive black hole at the centre of KUG 1208+386, a nearby galaxy that stopped forming stars about nine billion years ago. The Institute of Space Sciences in Spain announced the finding on Tuesday after its publication in Astronomy & Astrophysics, describing it as the first such outflow identified in a quiescent galaxy. The wind is moving at about 7% of the speed of light, or roughly 21,000 kilometres per second.
Ultra-fast outflows are highly ionized winds launched close to black holes while they consume surrounding matter. Astronomers usually find them in gas-rich galaxies that are actively making stars or only beginning to shut star formation down. The new result challenges that pattern because KUG 1208+386 has remained quiescent for billions of years even though its nucleus still contains an active black hole surrounded by dense material.
The international team combined archival X-ray observations collected by the European Space Agency's XMM-Newton observatory in 2009 and NASA's NuSTAR telescope in 2019 with optical spectra recorded by the Dark Energy Spectroscopic Instrument in 2022. The researchers identified the fast wind through its imprint on the X-ray spectrum and used the optical data to examine star formation and a much weaker outflow across the host galaxy.
According to the paper, the nuclear wind carries an estimated kinetic power of between 0.8 and 6.5 times 10 to the power of 43 ergs per second. That equals about 1% to 8% of the black hole's Eddington luminosity and greatly exceeds the roughly 10 to the power of 40 ergs per second measured for the galaxy-scale ionized outflow. The team also found that the black hole is obscured by thick gas along the line of sight and by even denser material around its nucleus.
The observations support a possible wind-driven form of maintenance feedback. Rather than causing the galaxy's original shutdown, intermittent winds from the still-feeding black hole might stop gas from cooling enough to restart star formation. This would add another mechanism to the radio jets that astronomers often invoke to explain how old galaxies stay dormant, while also suggesting that the immediate environment of a black hole matters more for launching such winds than the galaxy's overall gas supply.
Researchers cautioned that one galaxy cannot establish how common the process is. Their next step is to search a larger sample of quiescent galaxies for comparable outflows and determine whether KUG 1208+386 is exceptional. Comparing more systems should test which nuclear conditions produce the winds, whether host-galaxy properties change their strength, and how much they contribute to keeping galaxies inactive over billions of years.
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