Astronomers Reveal How 'Zombie Vortices' Help Birth New Stars

How are stars born? Apparently, it may have something to do with "zombie vortices." Scientists have created a new theory that may reveal how these vortices lead to the birth of a new star.

The first steps of a new star's birth involve dense clouds of gas collapsing into clumps. With the aid of angular momentum, these gas clumps spin into one or more Frisbee-like disks. After a time, a protostar begins to form. Yet for this protostar to become larger, the spinning disk needs to lose some of its angular momentum so that the gas can slow down and spiral inward into the protostar. Once this protostar gains enough mass, nuclear fusion can begin and a star is born.

While researchers know that this is generally how a star forms, though, it's been unclear how exactly the cloud disk sheds its angular momentum so that mass can feed into a protostar. Needless to say, without this step the protostar won't be able to grow large enough to form an actual star. That's why scientists decided to investigate star formation a bit further to better understand the forces at work.

"Current models show that because the gas in the disk is too cool to interact with magnetic fields, the disk is very stable," said Philip Marcus, one of the researchers, in a news release. "Many regions are so stable that astronomers call them dead zones--so it has been unclear how disk matter destabilizes and collapses onto the star."

More specifically, the current models fail to account for changes in a protoplanetary disk's gas density based upon its height. This particular change in density creates an opening for violent instability. That's why the researchers accounted for density change in their newest computer models.

So what did they find? It turns out that 3D vortices emerged in the protoplanetary disk, and these vortices spawned more vortices. This led to the eventual disruption of the protoplanetary disk's angular momentum.

"Because the vortices arise from these dead zones, and because new generations of giant vortices march across these dead zones, we affectionately refer to them as 'zombie vortices,' said Marcus. "Zombie vortices destabilize the orbiting gas, which allows it to fall onto the protostar and complete its formation."

The findings reveal exactly how newborn stars are formed. With the models, the researchers were able to find that these zombie vortices are largely to blame for the disruption of momentum which leads to material being drawn to the center of the protostar and the eventual birth of a star.

The findings are published in the journal Physical Review Letters.