A supernova.
A star the size of our Sun or smaller is too small to become a "Nova", so we can expect that the original brightness of a "nova" star is probably brighter than the Sun; possibly a lot brighter.
A nova is a star that suddenly increases in brightness.
A supernova.supernova
A supernova occurs AFTER a star collapses suddenly. See related question
Variable stars can brighten and fade in a regular pattern. A few reasons for this occurrence are shrinking and expansion, or the star's light being eclipsed by a companion object.
A Nova. The colossal explosion of a very large star at the end of its life is a Supernova.
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A star the size of our Sun or smaller is too small to become a "Nova", so we can expect that the original brightness of a "nova" star is probably brighter than the Sun; possibly a lot brighter.
A nova is a star that suddenly increases in brightness.
Yes.
Assuming you mean a "main sequence" yellow star, it's a white dwarf star. In the end that fades to a black dwarf.
As a star dies, its luminosity fades. It is in a sense the radiation that keeps it from collapsing. When the radiation fades beyond a certain point, the star collapses. The collapse releases a huge burst of energy and light and the star turns into a nova or supernova. At this point several things can happen. The star can turn into a black hole but other things can happen as well.
There are huge (several times the size of the earth) storms on the surface of the Sun, sometimes these cause gigantic flares to expand out from the surface of the star into space. These "flares" are said to "erupt".
Assuming you mean a "main sequence" yellow star, it's a white dwarf star. In the end that fades to a black dwarf.
NOVA
A supernova.supernova