Gas rivers feed a future star express
In the dark cloud G318.049+00.086, where no star has yet formed, dust and gas have arranged themselves into four long filaments. They converge into a dense central hub, like four rivers emptying into a lake. Gas flows along these filaments toward the center: the flow speed reaches 10–20 kilometers per second per parsec of length. This means that more than a thousand solar masses of material arrive at the hub every million years.
Inside the hub, astronomers found clumps — future stars. Most of them have emission profiles skewed toward the blue. Such a skew arises when the outer layers of a clump are falling inward, and we see only the near half. So these clumps are collapsing under their own gravity. But a few clumps showed a red skew: their gas is expanding instead.
This picture resembles a race where the winner is not the strongest but the one in the right place. Clumps on the filaments lose material, while the hub at the center accumulates it and will likely give birth to one or more massive stars. That's how giants are born — stars that later illuminate entire clusters.
Original abstract
as written by the authors arXiv:2602.01238
We present a gas kinematic study of the massive protocluster G318.049+00.086. The protocluster is reported to contain 12 prestellar core candidates and 4 protostellar cores. Filamentary structures are identified using the 1.3 mm dust continuum map, with four of them converge into a dense central region, forming a hub-filament system (HFS). High velocity gradients (10 - 20 km s$$^{-1}$$ pc$$^{-1}$$) derived from PV analysis of H$$^{13}$$CO$$^{+}$$ emission along three of those filaments are suggestive of mass inflow onto the central hub. A mass inflow rate higher than $$10^{3}$$ M$$_{\odot}$$ Myr$$^{-1}$$ along the filaments is indicating that the central hub is capable of forming massive star(s). Investigation of H$$^{13}$$CO$$^{+}$$ and CCH spectral profiles revealed the majority of the cores having the characteristic blue asymmetric line profiles, typical signature of gravitational collapse. The remaining few cores showed red asymmetric profiles, indicative of gas expansion. Also, the derived mass infall rates for the protostellar cores in hub-region is significantly higher in comparison to those located along the filaments. The mass-radius relationship of the cores revealed that the cores with red profiles reside in the massive star formation regime. However, the global velocity gradient along the filaments suggests that these particular cores are losing material to the hub. Our results are supporting a competitive accretion scenario of massive star formation where gas is expected to be funnelled from less gravitationally dominant cores to the cores located at the gravitationally favorable position.
The infall speed in this cloud is such that in a million years, a mass equal to a thousand Suns flows into the center. For comparison, our Sun will lose only a tiny fraction of its material over its entire lifetime.