In the quiet of cold molecular clouds, where interstellar gas under gravity condenses into dense clumps, the birth of massive stars is one of the great puzzles of astrophysics. One might think that the powerful radiation of a newborn giant would blow away surrounding matter, halting its growth. But observations paint a far more dramatic picture: instead of calmly accreting material from a protostellar disk, massive stars often emerge from dynamic catastrophes — close encounters and mergers of protostars. Imagine: two enormous gas balls collide, and at the moment of impact, gravitational energy is released, comparable to the total energy of a supernova. At the collision site, a local Big Bang ignites, scattering a fan of molecular streamers whose motion strikingly mirrors the expansion of the Universe.

Peer into the molecular emission map obtained via radio astronomical and spectroscopic methods at millimeter wavelengths. Dozens, sometimes hundreds of thin jets, like the taut strings of a giant harp, emanate from a single center. Their radial velocities, measured by red and blueshift, increase proportionally with distance from the epicenter — exactly as in Hubble's law, discovered by Edwin Hubble and Georges Lemaître for the entire Universe. Only here the 'Hubble constant' is 15 orders of magnitude larger, and the flow's age is not billions of years but mere thousands. Numerical simulations confirm: the released gravitational energy of the merger is just enough to impart the observed kinematics to the gas filaments. In some systems, additional effects of magnetic reconnection with acceleration of cosmic rays have also been noted.

The discovery of explosive molecular flows overturns the picture of how the most massive stars are born. The monotonous accretion is replaced by the turbulent dynamics of stellar clusters, where mergers are not the exception but the rule. This explains longstanding paradoxes: why massive stars are often single or in tight binary systems, and why their mass function has unexpected kinks. Moreover, local 'big bangs' become a natural laboratory for high-energy astrophysics: here we can study shock waves, gamma-ray production, and injection of matter into the interstellar medium. Soon, next-generation telescopes — JWST in the infrared and the under-construction ngVLA in radio — will conduct a massive census of these events and allow us to reconstruct in detail the physics of these fleeting cataclysms. Interestingly, the peak temperature in the shock wave can reach millions of degrees, producing soft X-ray emission — another greeting from the era of primordial nucleosynthesis.

And yet the most intriguing feature of explosive outflows is their Hubble-like kinematics. The local explosion exactly replicates the global expansion of the cosmos, hinting at the deep unity of natural laws. From the scale of a protostellar cloud a few light-years across to the scale of the entire Universe, the same recipe works everywhere: injected energy makes matter fly apart at a speed proportional to distance. Perhaps by studying these transient flares, we will not only understand how the Galaxy's brightest lights are kindled but also touch the first moments of our world's life.