Introduction

The Sun was formed roughly 4.5 billion years ago from the gravitational collapse of a gaseous cloud. The core of this cloud settled in the center, gathering an overwhelming fraction of the matter of the cloud (∼ 99.85%) while the rest formed a disk that would eventually turn into the solar system. Owing to gravitational forcing, the central mass gained temperature and the core, reaching a critical temperature of about 15 million K, began to undergo nuclear fusion. The present Sun is primarily composed of Hydrogen (∼ 71%) and Helium (∼ 27%), the rest being metals (in astrophysical jargon, elements other than Hydrogen and Helium are termed ‘metals’).