Final answer:
The formation of a planetary nebula is never a consequence of a supernova explosion, which instead can trigger star formation, create neutron stars, and emit neutrinos.
Step-by-step explanation:
The question asks which phenomenon is never a consequence of a supernova explosion. The correct answer here is the formation of a planetary nebula, which is not a result of a supernova explosion but is rather created when a low or intermediate-mass star dies and sheds its outer layers. On the other hand, triggering of star formation by shock waves, condensation of matter into a solid nuclear star composed entirely of neutrons (a neutron star), and the generation of a pulse of neutrino emission are all consequences of supernova explosions.
Supernovae contribute to nucleosynthesis, producing elements heavier than iron and dispersing them into space, which is essential for life on Earth. These explosions can also lead to the formation of neutron stars, which may be observed as pulsars if their radiation beams point toward us. Additionally, neutrinos play a crucial role in the supernova process, helping to initiate the explosion and affecting the dispersal of the heavy elements necessary for life.