A supernova occurs when?

• A. A planet gradually cools and fades away.
• B. A star ends its life and explodes in a burst of light.
• C. A galaxy collides with another.
• D. A nebula dissipates without any explosion.

Answer: (B)

A supernova is a massive stellar explosion that marks the end of life for certain stars. In the most common case, a massive star runs out of fuel, its core collapses under gravity, and the outer layers are blasted outward in a colossal explosion, releasing an immense burst of light and creating new heavy elements. Another route is a white dwarf in a binary system pulling in material until it reaches a limit and undergoes a thermonuclear runaway, also resulting in a brilliant explosion. This event is fundamentally about a star ending its life in an explosive release of energy and matter, not about a planet cooling, a galaxy colliding, or a nebula simply dissipating.