B171 Nebula
   A nebula is an interstellar cloud of dust, hydrogen, helium and other ionized gases. Originally, nebula was a name for any diffuse astronomical object, including galaxies beyond the Milky Way. The Andromeda Galaxy, for instance, was referred to as the Andromeda Nebula before the true nature of galaxies was confirmed by astronomers in the early 20th century.
    Nebulae are often star-forming regions. This poster shows NASA images of some of the most famous colorful. The famous "Pillars of Creation" is shown in the lower right corner. It is perhaps the most famous of all NASA photographs. 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.