Nova in Scorpius. The position of this nova, 1737-34 Nova Scorpii 1, is shown by the cross- hairs. A nova is a huge brightening of a double star system, which makes a previously unseen star visible for a short time. It occurs when one star is a small, dense white dwarf and the other is much larger. The white dwarf accretes hydrogen gas from the larger star onto its surface. Once a specific amount of hydrogen has accreted, it becomes dense enough for nuclear reactions to begin, and it ignites. This blows away the remaining gas layers, so the brightening is short- lived, usually only lasting a few days. This nova was discovered on 25th July 2005.