Researchers propose a new theory of star formation

Researchers at the California Institute of Technology in the US have discovered that one in every 10,000 stars may be made out of metal.

Astrophysicist Philip Hopkins and his team decided to analyse how a phenomena of turbulence called preferential concentration affects star formation. 

Prefential concentration affects the way dense particles cluster, and it has been shown to have an influence in almost everything, from aerosol production to rain formation.

Turbulent flows are made out of different-sized eddies (think of them as mini whirlpools) that rotate at different speeds. Because these eddies spin at different rates and the particles contained in them are influenced by the speed, the place in which the particles cluster will vary according to their mass. If the “turbulent flow contains particles that are the same scale as the eddies”, explains Mark Strauss from io9, “they are pushed into regions between the vortices.”

In Hopkins’s model the eddies are gas clouds—supernova remnants—that contain many elements, including hydrogen, helium, lithium and heavy elements.

Physics arXiv Blog explains that “preferential concentration tends to force the heavier elements out of regions of high vorticity so that they become concentrated in the gaps between the eddies. This concentration of mass creates a stronger gravitational field which attracts more mass and so on. So in Hopkins's new model of gas clouds, preferential concentration becomes an important trigger of star formation.”

Because the heavy elements were separated from the others, some stars made in these regions [the gaps between the eddies] are made entirely of elements other than hydrogen, helium and lithium, explains Physics asXiv. "Put another way", explains Strauss from io9, "turbulence can pluck out particles that share the same specific mass and concentrate them together." This mean some stars exhibit what astronomers call metallicity, which means they are made of elements heavier than hydrogen and helium, such as iron.

So, as Hopkins suggests in his paper, some stars must be made entirely out of metal.

So far no one has spotted one of these shiny stars, but we’re sure astronomers will now be trying to find them.