Ais a collection of stars, dust, and gas bound together by gravity.

Your answer is galaxy.

Explanation:

The official description of a galaxy is "a system of millions or billions of stars, gas, and dust, that are held together by a gravitational pull. Hope this helped!

italian workers migrated to northern provinces

a mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics. this uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.a geomagnetic reversal is a change in a planet's magnetic field such that the positions of magnetic north and magnetic south are interchanged.