Our planet, Earth lies with our Solar System which itself is part of our home Galaxy, The Milky Way. A galaxy is a massive, gravitanionally bound system consisting of stars, stellar remnants, and interstellar medium of gas and dust, and, it is hypothesized, an important but poorly understood component, dark matter. The word galaxy is derived from the Greek, literally “milky”, a reference to the. Examples of galaxies range from with as few as ten million stars to giants with a hundred trillion stars, each orbiting their galaxy’s own center of mass.