Answer:
1- Neutron star --- The dense remains of a star
2- Nebula --- A large mass of gas and dust
3- Supernova --- An explosion of a star
Step-by-step explanation:
1- A neutron star is a type of stellar remnant resulting from the gravitational collapse of a massive supergiant star after exhausting the fuel in its core and exploding as a supernova. As the name suggests, these stars are composed mainly of neutrons.
2- Nebulae are regions of the interstellar medium constituted by gases (mainly hydrogen and helium) as well as chemical elements in the form of cosmic dust.
3- A supernova is a stellar explosion that can manifest itself in a very remarkable way, even to the naked eye, in places on the celestial sphere where previously nothing had been detected in particular.