Nebula are clouds of interstellar hydrogen and other gasses that span light years. Some may be dozens or hundreds of light years across.
Galaxies were once referred to as nebula. These are vast collections of stars, often a hundred thousand light years in diameter (as is our own beloved Milky Way) or more.
Emission nebula glow and reflection nebula reflect the light form other stars
See related link
The oldest known nebula is the Cassiopeia A supernova remnant, which is estimated to be around 330 years old in human terms since its explosion was observed in the 17th century. However, in terms of its material, the remnants may contain elements formed in previous stars that are billions of years old. Other ancient nebulae, like the planetary nebulae, can also contain stellar material that is over 10 billion years old, stemming from the early universe. Thus, the age of nebulae can vary widely depending on how one defines "oldest."
An absorption nebula is a dark nebula, which absorbs all incident radiation without reemission.
Another popular nebula is the Eagle Nebula, also known as Messier 16. It is located in the constellation Serpens and is famous for the "Pillars of Creation," which are towering columns of interstellar gas and dust where new stars are forming.
nebula
The Stingray Nebula (Hen 3-1357) is a planetary nebula. (The youngest known).
"The Crab" is a nebula.
a type of nebula
A cloud in outer space consisting of gas or dust and planetry nebula is one of the types also called ring nebula or A planetary nebula is an emission nebula consisting of a glowing shell of gas
The Helix Nebula is a planetary nebula located in the constellation Aquarius, while the Ring Nebula is a planetary nebula located in the constellation Lyra. The Helix Nebula appears more like a disk or helix shape, while the Ring Nebula appears as a ring or donut shape due to its orientation.
Emission nebula glow and reflection nebula reflect the light form other stars
The crab nebula.
protostar or nebula
The eye of god is a Helix nebula. Close to a Planetary nebula.
See related link
It is called a Nebula (nebulae for plural). no sorry but your wrong it is a coma It can be both it just depends. The question needs to be more specific