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Gravitational Collapse in the Presence of a Magnetic Field

1966; Oxford University Press; Volume: 132; Issue: 2 Linguagem: Inglês

10.1093/mnras/132.2.359

1365-2966

P. A. Strittmatter,

Astro and Planetary Science

The effect of a frozen-in magnetic field on the gravitational instability of a primeval gas cloud is examined by means of the scalar and tensor virial theorems. It is shown in particular that the critical mass, below which a cloud is unable to contract indefinitely across the lines of force under its own gravitational field, is reduced by a factor ∼0.5 if the cloud becomes highly flattened due to flow of material down the field lines. For a cloud of given mass, it is found that a change by a factor ∼4 in magnetic flux will account for the difference between the possibility of complete gravitational collapse and the establishment of an equilibrium position at almost (within 1% of) the original lateral dimensions of the cloud. The possible effects of rotation and thermal energy, in the presence of a magnetic field, are briefly discussed.