Do you mean a nova? A Nebula is a large group of stars and dust in the sky. e.g. the Orion nebula. An individual star would not ordinarily change into a nebula, but the Crab Nebula is one such, first seen on earth about 1054 CE. But it had taken about 6500 years for the light to reach us. If your query was about nova or supernova, ask again.
A nebula contains stars and other matter; a supernova is just a large enough nova, or star that explodes at the end of its life cycle due to spent fuel
in what part of the constellation Orion is the Orion nebula located at
Planetary nebulae (the cat's eye nebula) Emission nebulae (the orion nebula) Dark nebulae (the horsehead nebula) Supernova remnant nebulae (the crab)
The Orion nebula is about 1,345 light years away.
Orion is a constellation made up in the minds of the ancients to represent "Orion" a hunter in mythology. The Orion Nebula is a diffuse nebula located south or Orion's belt. It is an area of extensive star formation. It is only called Orion Nebula as it is seen within the constellation of Orion. See related questions
As the Orion Nebula is visible with the naked eye, the only sensible answer would be "by looking at it".
A nebula does not explode. A nebula is generally the remains of a supernova explosion.
Triffid Nebula, Eagle Nebula, Cat's Eye nebula
The Crab Nebula is a supernova remnant and pulsar wind nebula.
Not surprisingly - Orion!!