A Galaxy Breathes Out: How a Wind Is Born from Stars express
Two galaxies collided, and from their center an invisible fountain erupts. The ALMA and VLT telescopes peered into the heart of the IRAS20100-4156 system — where two stellar islands are merging. There, work is in full swing: hundreds of new suns are being born, and their heat drives a stream of cold gas outward.
This stream is like a giant's exhale. It carries away nearly half of all the molecular gas — the very raw material from which new stars could have formed. The wind's speed is 170 kilometers per second. Each year, it ejects a mass equivalent to 700 suns. If this continues, the entire gas reservoir will be depleted in 16 million years — a blink of an eye by cosmic standards.
The most surprising thing: the stream doesn't slow down. Usually, a wind weakens as it travels away from its source. Here, at a distance of five thousand light-years, it's still moving at the same speed. Something continues to push it. Most likely, it's light from millions of hot stars: it presses on dust grains and gas like wind on a sail.
The stream emerges as two cones — above and below the galaxy's plane. It's like a jet from a hose when you pinch the opening. The cones' direction aligns with the galaxy's rotation axis — meaning the wind breaks through where resistance is lowest.
This 'exhale' is not just a pretty sight. It decides the galaxy's fate: the expelled gas will never become stars. Perhaps this is how 'dead' elliptical galaxies are born: those where new stars no longer ignite. By observing IRAS20100-4156, we see a galaxy extinguishing its own stellar fire.
Original abstract
as written by the authors arXiv:2601.20489
We use ALMA CO(1-0) observations and VLT/MUSE rest-frame optical data of the ultraluminous infrared galaxy (ULIRG) IRAS20100-4156 at $$z=0.1297$$ to characterize its powerful outflow in multiple phases using tracers of cold molecular, ionized, and neutral atomic gas and dust as well. Our analysis uses the correspondence with the stellar velocity field to split the complex emission line profiles of the CO(1-0) line into components in gravitational and non-gravitational motion. We find a massive ($$8\times10^{9}\,M_\odot$$) molecular outflow containing about 40% of the total molecular gas mass in the system. The outflow shows a bi-conical morphology centered on the brightest galaxy in the merger, oriented along its minor axis and extending to $$\sim5\,\mathrm{kpc}$$. This outflow has a characteristic velocity of $$170\,\mathrm{km/s}$$, an outflow mass rate of $$700\,M_\odot/\mathrm{yr}$$, a depletion time of $$16\,\mathrm{Myr}$$, and energetics consistent with star formation as a driver. The neutral atomic and ionized gas phases traced by NaI absorption and H$$\alpha$$ emission show counterparts to the blueshifted cold molecular outflow but are only 15% and 3% as massive. None of the three gas phases show any signs of slowing down over the extent at which we detected the outflow, suggesting an acceleration mechanism acting on the outflowing gas at kiloparsec scales. We also detect $$3.5\times 10^7\,M_\odot$$ of dust, traced by optical extinction in the MUSE data, in the blueshifted outflowing cold molecular gas. The ionization state of the non-outflowing gas is consistent with star formation, while the outflowing component shows shock-like ionization. We conclude that the multiphase outflow in IRAS20100-4156 originates in the southeast nucleus of the merger and is driven by the starburst activity there, with radiation pressure likely playing a significant role in its acceleration.
The speed of this galactic wind is 170 km/s. That's 500 times faster than the fastest airplane and 15 times faster than a rocket at launch.
In Stanislaw Lem's novel 'Solaris', the planet's ocean also ejects streams of matter into space — though for entirely different reasons.