This “river” is the Magellanic Stream, an extended hydrogen cloud that links the Galaxy to the Magellanic Clouds and a number of dwarf galaxies. The total mass of the cloud is probably more than a thousand solar masses. On the celestial sphere, the Magellanic stream stretches from the constellation Pegasus to the constellation Sculptor through the southern galactic pole.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.