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A neutron star was found to have a dense, fog-like wind — a discovery that challenges current theories.
When a companion star pulls matter onto a neutron star, a whirlwind of scorching gas swirls around it. From this, streams erupt — a stellar wind. It was thought that with bright radiation, the wind should race at nearly the speed of light. But the XRISM telescope, examining the light with spectroscopy, showed otherwise.
The wind from GX 13+1 turned out to be not a hurricane, but a dense fog: record-breakingly thick and unexpectedly slow. A speed close to light was expected, but the stream moves thousands of times slower. This can't be explained by light pressure — it's likely pushed out by heating of the outer disk regions.
The dense fog dims the star's visible brilliance, making it fainter.
The discovery forces a rethink of how neutron stars and black holes return matter to the galaxy, influencing the birth of new stars. The contrast with winds from supermassive black holes, flying nearly at light speed, emphasizes that both fog and hurricane coexist in space.
Neutron stars were theoretically predicted by Fritz Zwicky in 1934, and the first observational confirmation came in 1967 when Jocelyn Bell Burnell discovered pulsars.
The optical depth for electron scattering is proportional to the hydrogen column density and the Thomson cross section; the factor 1.21 accounts for the number of electrons per hydrogen atom in a fully ionized plasma of solar composition.
