The term 'Astronomical Flare-up' can be broken down into two words, 'NOVA' and 'Flare-up'. A NOVA is a type of stellar explosion that occurs in a binary star system when one of the stars begins to draw matter from its companion star. This matter accumulates on the surface of the star until it reaches a critical mass and then explodes, releasing a large amount of energy. A flare-up is an increase in intensity or activity, so an Astronomical Flare-up is an increase in the intensity of a NOVA.