Since,Nebula is an interstellar cloud of dust, hydrogen gas, helium gas and other ionized gas so it's antonym can be clearness and brightness
Emission nebula glow and reflection nebula reflect the light form other stars
See related link
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.
The Andromeda Nebula was created in 1967.
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
Emission nebula glow and reflection nebula reflect the light form other stars
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.
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