B171 Galaxies
   A galaxy is a massive, gravitationally bound system consisting of stars, stellar remnants, an interstellar medium of gas and dust, and dark matter, an important but poorly understood component.  A The word galaxy is derived from the Greek galaxias, which means "milky", a reference to our own Milky Way galaxy. They vary vastly in size from dwarfs that contain a few as ten million stars to the giants with over a hundred trillion stars. Each orbits it own centers of mass. This poster shows 15 NASA photographs carefully selected from the great many available to show the diversity of these amazing systems. Each is accompanied by an explanatory caption.
    Nebula and galaxies are similar in that they are enormous systems of space materials. The big difference is that everything in galaxies is in orbit around a central mass. Nebula have no "center of gravity" so everything just floats around, going its own way.

STATUS: The above poster is complete. Due to their similarities is is anticipated that Nebula and Galaxies may be published at the same time. No publication date has been established.