Why might a very bright fireball appear much larger than the actual meteoroid causing it?

Answer

Because the light is created by superheating the air around the object, forming a glowing coma

A very bright fireball can appear larger because the light is generated by the superheating of the air surrounding the vaporizing object, often resulting in a glowing 'head' or coma that exaggerates the perceived size.

Why might a very bright fireball appear much larger than the actual meteoroid causing it?
Meteorastronomyfireball