An object in the sky brightens suddenly,but shows no hydrogen lines in its spectrum.It is most likely a(n):
A) comet.
B) type I supernova.
C) type II supernova.
D) asteroid impact.
E) stellar collision.

Question

Quizplus · Accepted Answer

The fact that there are no hydrogen lines in the spectrum suggests that the brightening is not due to a normal star or a comet, both of which would have hydrogen in their atmospheres. An asteroid impact or stellar collision would also not produce the sudden brightening that was observed. A type II supernova is associated with the explosion of a massive star and would be expected to have hydrogen lines in its spectrum. Type I supernovae, on the other hand, are thought to be the result of a white dwarf star in a binary system exploding and do not have hydrogen lines in their spectra. Therefore, the sudden brightening with no hydrogen lines in the spectrum is most likely due to a type I supernova.

An Object in the Sky Brightens Suddenly,but Shows No Hydrogen