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Magnetic Waves Affects The Process Of Star Formation

[Estimated read time: 3 minutes]
  • A new study explains the phenomenon that sets the properties of stars and their orbiting planets.
  • Using simulations, researchers tracked wind material as it interacts with the ambient cloud.
  • They deduced that winds and radiation emitted by stars are responsible for significant energy transfer within molecular clouds – an impact enhanced by magnetic waves.

The evolution of molecular cloud, stars and even the properties of stars depend on supersonic turbulence from the interstellar medium. However, motions from these turbulence decay quickly.

It is an extreme environment where everything happens at once, such as gravitational collapse driving turbulence and stellar feedback (energy ejected from forming stars) sustaining turbulence. So far, no direct connection between interstellar turbulence and star formation has been reported.

Although numerous numerical studies have shown that stellar feedback could maintain turbulence on parsec scales when the process of star formation is at peak, none of these studies differentiate between non-interacting gas, gas entrained and removed by stellar feedback.

Recently, researchers at the University of Texas at Austin discovered that magnetic waves play a crucial role in the star formation process within gigantic clouds. The study explains the processes that set the properties of stars, which further impacts the formation of planets orbiting these stars.

Magnetohydrodynamic Simulations

Since it’s quite impossible to observe these clouds via telescopes, researchers used computer models to separate the various influence of different processes that contribute to star formation. To analyze each and every aspect they developed models of clouds with magnetic fields, gravity, and stars on a supercomputer.

They focused on stellar winds because the cloud energy is comparable to stellar wind energy but these winds are not enough to disperse the cloud. They also examined multiple magnetohydrodynamic simulations of stellar sources within turbulent clouds.

star formation via magnetic waves 2 turbulent clouds with (right) & without stars (left). Colors indicate gas speed: red (250 km/s), blue (25 km/s), and grey (10 km/s). | Credit: Stella Offner 

All simulation features a turbulent molecular cloud with an initial gas temperature of 10 Kelvin, gas density of 2×10g cm-3, and a total mass of 3762 times solar mass. Then they randomly inserted 5 stellar sources, representing either older stars formed in a nearby cloud or young giant stars. Now, the simulations had 2 stellar distribution, turbulence pattern of 4 different magnetic field strengths and computations with and without gravity.

Reference: Nature Astronomy | doi:10.1038/s41550-018-0566-1 | University of Texas

Overall, the simulations demonstrated that interaction between cloud magnetic fields and stellar winds produces energy and influences gas over a larger area across the cloud than previously considered.

You can imagine magnetic fields as rubber bands stretched across the cloud. Winds pushing the field is similar to plucking the rubber band. The wave outruns stellar winds and causes motions at greater distances.

They concluded that magnetosonic wave excitation is alone enough to offset a major fraction of the turbulent dissipation. Although the rate of turbulent dissipation, the mass of cloud, source properties, and magnetic field are highly uncertain, it constitutes exceptional agreement and shows that feedback could slow gravitational collapse and replenish turbulence in star-forming clouds.

Reference: The First Snapshot Of Newborn Planet Around The Young Dwarf Star

In the next study, authors will investigate the star-forming process on massive scales, both in space and time. While the present research focuses on a single area of star-forming cloud, the future study will analyze the magnetic field and feedback effects on scales bigger than one cloud.

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