Space is full of dust. Its tiny particles, a billion times smaller than a grain of sand, race through the void. Some look like ground sand: these are silicates (containing silicon and oxygen). Others resemble soot: these are carbon with hydrogen. Normally they don’t mix. But stellar explosions can propel them at tens of kilometers per second, and then things get interesting.
The collision works like a mill. Slow speeds: grains bounce off like peas off a wall. A bit faster: they stick together into a clump. At high speeds, they shatter, and the fragments instantly combine into new substances. The threshold for this shattering is about 7.5 kilometers per second. Above that, carbon dust yields hydrocarbons (chains of carbon and hydrogen), while silicate dust yields silicon-oxygen compounds. Even more complex molecules appear, such as aldehydes — chains of carbon, hydrogen, and oxygen.
Thus the cosmic mill turns inert dust into organic 'semi-finished products'. These molecules can later become part of new stars and planets. It turns out that destruction in space often goes hand in hand with creation.
In simulations at high speeds, exotic chains of pure carbon up to eight atoms long sometimes emerged — molecules such as l‑C₃ and C₅, previously found in the atmospheres of cool stars and in molecular clouds.