The Magellanic Stream and the mass of our Hypergalaxy

The kinematics of the Magellanic Stream and of other high velocity clouds is investigated. Arguments are presented to show that they are permanent members of the system of companions of our Galaxy. Using the kinematics of high velocity clouds and of other high velocity objects as well as the spatial distribution of the companions of the Galaxy, the virial theorem mass of our Hypergalaxy (the subcondensation of galaxies and intergalactic matter around the Galaxy in the Local Group) is estimated: $${M}_\text{tot}\,=\,(1\cdot2\pm\,0\cdot5)\,\times\,{10}^{12}\,{M}_{\odot}$$. It is shown that essential observed properties of the Magellanic Stream (change of velocities, densities and angular size along the Stream) are consistent with the hypothesis that clouds of the Stream are moving around the Galaxy along elliptical orbits $$({R}^\text{min}\,\approx \,14\,\text{kpc},\,{R}_\text{max}\,\approx \,100\,\text{kpc}$$.