Nebula is cloud of gas and dust
Nebula is an interstellar cloud of dust, hydrogen, helium and other ionized gases. It is the name for any diffuse astronomical object, including Galaxies beyond the Milky Way. For instance, the Andromeda Galaxy, also called the Andromeda Nebula. Most of them are huge in size, hundreds of light years in diameter, denser than the space that surrounds them. These are often regions of Star formation such as the Pillars Of Creation in the Eagle Nebula. In these regions there is a gas, dust and other materials that are collected together and form larger masses. That attract additional material and eventually become massive enough. In the middle of the gravitational collapse of gas forming Nebulas and Stars. Remaining materials form the Planets and other objects of planetary systems. Some are formed as a result of Supernova explosions. In fact, the death of massive short lived Star. The ejected material from the Supernova explosion are ionized by the energy and created the compact object. ...