When we look at distant galaxies, we sometimes see dazzlingly bright lights at their centers: these are quasars. In essence, they are shimmering swirls of gas falling into enormous black holes, whose nature was first described by Karl Schwarzschild. But many quasars in the early Universe, a couple of billion years after the Big Bang, when everything around had already filled with dark matter, hide behind thick dusty veils, like a bright lamp under a dense dusty cloth. Light tries to break through, but dust weakens and changes it.

A new study has precisely caught the moment when powerful gas winds blowing from the black hole blow away this dusty cocoon. Using spectroscopy, a method that breaks light into its colors, astronomers measured the speeds of these winds: they reach 16% of the speed of light! For comparison: in one hour, such a flow would cover the distance from Earth to the Sun more than three times. Interestingly, the dust in these winds turned out to be very fine, like flour rather than sand — shock waves grind large dust grains into the finest powder. That is why the light from the quasar, passing through this suspension, loses some of its colors: the lines of carbon and helium are barely visible, while the Hα line of hydrogen, discovered by Johann Balmer, stands out clearly.

This 'shedding' is a critical moment in the life of a quasar. Previously, we didn't understand how dust-hidden objects turn into unclouded bright ones. Now it's clear that the stage with powerful winds and weak lines fills the gap. In essence, we are witnessing how a quasar frees itself and begins to affect its entire host galaxy, regulating the birth of new stars. In the future, the James Webb Space Telescope will be able to examine these dusty dramas in even greater detail in infrared light, which is currently hard to probe.