Nova

Transcript: Consider a binary pair where the more massive star has expanded to fill its Roche lobe, and the smaller star is a white dwarf of nearly 1.4 solar masses. As the massive star dumps hydrogen onto the white dwarf the gas is compressed, rapidly heated, and it ignites nuclear reactions that blow off a shell of gas. The resulting emission is called a nova. This process is cyclic because gas can then accumulate again, and on a time scale ranging from a hundred to ten thousand years a new cycle of gas flow, compression, ignition, and blowing off occurs. It’s not exactly periodic, but the flaring up of a star in a nova event is spectacular because the brightness can increase by several orders of magnitude. Roughly thirty to fifty novae are seen per year among the several hundred million stars in the Milky Way galaxy. Nova stands for new stars; these are some of the most prominent events in recorded history in astronomy.