The Sun is the roundest natural object ever measured
Satellites measuring the Sun's shape found it bulges at the equator by just eight parts per million, less than expected. That makes it the closest thing to a perfect sphere nature has ever shown us, even though it spins faster at its middle than at its poles.
The Sun holds about 99.86 percent of the Solar System's mass, some 330,000 times Earth's, and spans roughly 1.39 million kilometres, about 109 Earths across. Its light takes around eight minutes to reach us, and the average gap between the two bodies defines the astronomical unit. Every second its core fuses roughly 600 billion kilograms of hydrogen into helium and turns four billion kilograms of matter into energy. It is a G2V star, outshining around 85 percent of the galaxy's stars, the bulk of them dim red dwarfs.
It formed about 4.6 billion years ago from a collapsing patch of a molecular cloud, perhaps nudged by shockwaves from nearby supernovae; the Solar System's generous supply of gold and uranium hints at that. Most of the gas fell to the centre, and the rest flattened into the disc that became the planets. Since then the helium share in the core has climbed from about 24 percent to about 60, and because the core passes heat outward by radiation rather than convection, that helium stays put.
Its spin is uneven. Relative to the stars, the equator turns in about 25.6 days and the poles in about 33.5, a difference driven by convection and the Coriolis effect. The young Sun probably spun up to ten times faster, with sunspots covering 5 to 30 percent of its face, until its magnetic field, tugging on the solar wind, slowed it down. The core still keeps a trace of that early pace, turning about once a week.
In four to seven billion years, as core hydrogen fusion falters, the Sun will swell into a red giant, then shed its outer layers as a white dwarf that may glow for trillions of years before fading into a black dwarf. Its English name comes from Old English sunne, while solar traces back to Latin sol.
Source: Sun
