“It’s not a guaranteed thing to have phosphorus abundant everywhere, ripe for the picking,” Cigan told Live Science. “It seems to look like luck plays a bigger role in this.”

Some of that luck may come down to size. The star that created Cassiopeia A is roughly twice as massive as the one that made the Crab Nebula. A more massive star could have generated different reactions that produce more phosphorus, the researchers said.

If the production of phosphorus varies widely across the galaxy, so might the likelihood of life on other planets. Even if a planet had every other condition required for habitability, it might still be bereft of life because it formed where there was a dearth of phosphorus, the researchers said.