The Sun Ignites
4.6 billion years ago, a cloud of gas and dust — the remnants of older dead stars — collapsed under its own gravity. At its core, the pressure became so extreme that hydrogen atoms began fusing. Our Sun switched on.
A nuclear reactor 150 million kilometres away
The Sun is a nuclear fusion reactor 1.4 million kilometres wide — 109 Earths lined up side by side. Every second, it converts 600 million tonnes of hydrogen into helium, releasing the energy equivalent of 10 billion nuclear bombs. That energy takes about 100,000 years to travel from the Sun's core to its surface, then just 8 minutes to reach Earth.
Where the Sun came from
The Sun formed from a nebula — a cloud of gas and dust left behind by previous generations of stars. About 4.6 billion years ago, something triggered this cloud to collapse inward, possibly a nearby supernova shockwave. As it collapsed, it spun faster (conservation of angular momentum), flattening into a disc. The centre became the Sun. The remaining disc became the planets.
How long it will last
The Sun is about halfway through its lifespan. In roughly five billion years, it will exhaust its hydrogen fuel and expand into a red giant, swallowing Mercury, Venus, and possibly Earth. Then it will shed its outer layers, leaving behind a dense, cooling white dwarf about the size of Earth. Long after that, it will slowly fade to black.
The Sun is not quiet
Solar flares and coronal mass ejections — massive eruptions of charged particles — regularly blast out from the Sun's surface. These affect satellites, GPS, power grids, and radio communications. They also create the aurora borealis. AwareStation monitors solar radio bursts using software-defined radio. The Sun is genuinely loud if you know what frequency to listen on.
The Sun's energy output is not perfectly constant. Slight variations in solar output over long timescales have influenced Earth's climate. The Maunder Minimum — a period of reduced sunspot activity from 1645 to 1715 — coincided with the Little Ice Age in Europe. The connection between solar activity and Earth's climate is real but smaller than human-caused climate change by several orders of magnitude.