Here's why:

* Nova: A nova is a sudden brightening of a star due to a thermonuclear explosion on its surface. This explosion is caused by the accretion of material from a companion star. The Orion Nebula does not have a single star that is undergoing a nova.

* Supernova: A supernova is a much more powerful explosion that occurs at the end of a star's life. It's often caused by the collapse of a massive star's core. The Orion Nebula is a vast cloud of gas and dust where stars are actively forming, not dying.

The Orion Nebula is a diffuse nebula, a vast cloud of gas and dust where stars are born. It's an active star-forming region, with many young, hot stars embedded within it.

The bright light and colors of the Orion Nebula are due to the intense radiation and stellar winds from these young stars, which are ionizing and illuminating the surrounding gas and dust.