Illustration of the recurrent nova system RS Ophiuchi. This binary system consists of a white dwarf star and a red giant star. The strong gravitational force of the white dwarf pulls gas from the red giant onto its surface, heating it. When the white dwarf's surface reaches over 10 million degrees Celsius a thermonuclear explosion is triggered. In this system that happens roughly every 20 years. The majority of the element lithium found in the universe is produced by novae explosions. RS Ophiuchi in the constellation of Ophiuchus, approximately 5,000 light-years from Earth.