Here's why:
* Irregularity: Nebulas are vast clouds of gas and dust, already incredibly diverse in shape and density. They aren't uniform, and their collapse isn't symmetrical.
* Gravity: The collapse is driven by gravity, pulling material towards the densest points. This creates a dynamic, constantly evolving shape. Imagine a cloud of smoke pulled inwards, with uneven clumps forming.
* Rotation: Many nebulas rotate, further complicating the shape as material gets pulled inwards and flattened along the axis of rotation.
* Magnetic Fields: Magnetic fields also play a role, influencing the flow of gas and dust.
What we do see:
* Flattened Disks: As the nebula collapses, it often forms a flattened disk. This is due to the interplay of gravity, rotation, and magnetic fields.
* Jets and Outflows: As material falls inward, some is ejected outward, creating jets and outflows of gas. These can create impressive structures, often observed in young stars.
* Protostars: At the heart of the collapsing nebula, a protostar begins to form. It can be surrounded by a rotating disk of material, feeding it as it grows.
Think of it this way: A collapsing nebula is like a chaotic, swirling dance of gas and dust, gradually forming into a more structured system with the eventual birth of a star. The exact shape it takes during this process is constantly changing, depending on the initial conditions and the forces at play.
