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Tides, torques and the timing argument

1989; Oxford University Press; Volume: 240; Issue: 2 Linguagem: Inglês

10.1093/mnras/240.2.195

1365-2966

Somak Raychaudhury, D. Lynden–Bell,

Geophysics and Gravity Measurements

The quadrupolar component of the gravitational field due to neighbouring galaxies at the barycentre of the Local Group is estimated. The tidal effect consists of an almost equal compression and extension along two principal axes, and of almost no effect along the third. The positive axis of the quadrupole component is aligned with the dipole component for galaxies within 10 Mpc of the Local Group. The nature of the binary orbit of the Andromeda galaxy and the Milky Way in the presence of this tidal field is investigated, and possible orbits are suggested. Though the tidal effects are appreciably strong, they hardly affect the mass of the Local Group derived from timing arguments. The direction along which Andromeda seems to have emerged from the Big Bang indicates that it was responsible for the orbit of the Magellanic Clouds about the Galaxy. The proper motion of Andromeda is predicted.