Making planets isn't easy*.
Stars form in the centers of disks of material that can stretch for many tens of billion of kilometers. The stuff from the disk falling into the center forms the star, but farther out where it's cooler is where planets tend to form. Usually, for stars this young planetesimals — chunks of rock and metal and ice from 1–100 km in size — likely dominate, the precursors to actual planets.
But a lot can go wrong. Too close to a star and it gets cooked. Too far and there may not be enough material to gather to create an actual planet.
The neighborhood matters, too. Most stars form in open clusters, some with tens of thousands or more stars. Astronomers have thought for some time that just where the star is located in the cluster makes a big difference in whether it can form planets or not, and that conjecture now has new support from a series of observations of a huge, relatively nearby cluster.
First, oh my, let me show you the cluster, because wow. Behold, Westerlund 2:
A Hubble of the huge star cluster Westerlund 2 reveals tens of thousands of stars, as well ...