Novas

Sometimes stars brighten drastically, becoming as much as 100 times brighter than they were. These stars are called novas (Latin for 'new stars'). They are not really new, just much brighter than they were earlier.







A nova is a binary, or double, star in which one member is a white dwarf and the other is a giant or supergiant. Matter from the large star falls onto the small star. After a thick layer of the large star’s atmosphere has collected on the white dwarf, the layer burns off in a nuclear fusion reaction.




The fusion produces a huge amount of energy, which, from Earth, appears as the brightening of the nova. The nova gradually returns to its original state, and material from the large star again begins to collect on the white dwarf.