Every second, the Sun loses 4.26 million tonnes of its own mass just to keep shining. Enter your age and find out how much of the Sun your lifetime has cost.
The Sun is not burning. Fire is a chemical reaction; the Sun is a nuclear one, and it is the difference between burning a log and dissolving a mountain. Deep in the Sun's core, hydrogen atoms are being squeezed so hard that they fuse into helium. When they fuse, a tiny bit of mass simply disappears and becomes light. Einstein's E=mc² makes the Sun shine. The bill is paid in body weight.
Every single second, the Sun loses about 4.26 million tonnes of its own mass. That is 4.26 billion kilograms per second, turned directly into light. To give you a sense: that is the mass of a mountain range, gone, every tick of the clock. Your whole lifetime, if you live to 80, costs the Sun about 10.7 quadrillion tonnes of itself. In more useful units: roughly 53,000 Mount Everests, or 500,000,000,000,000,000 copies of you.
The Sun has been paying this bill for 4.5 billion years. Over that time it has converted about 100 Earth masses of itself into light. That sounds like a lot. It is. But the Sun is enormous — 333,000 times the mass of Earth — so even after all that spending, it has lost only about 0.03% of itself. It can keep paying for another 5 billion years. The tab does not worry it.
Here is the strange part: every photon you have ever seen in sunlight spent hundreds of thousands of years escaping the Sun's core before finally getting out, then made it to your eye in 8 minutes. The warmth on your skin is the Sun's mass, converted and mailed across 150 million kilometers. You are warmed by the Sun's body weight. It is the most expensive heating bill in the universe, and it is paid by the star itself.
No. Burning is a chemical reaction with oxygen. The Sun fuses hydrogen into helium in its core. The fusion releases energy because the helium nucleus is slightly lighter than the four hydrogen nuclei that made it. The missing mass becomes energy, per E=mc².
About 4.26 million tonnes (4.26 × 10⁹ kg). This comes from the Sun's luminosity: L = 3.828 × 10²⁶ W, divided by c². Over 4.5 billion years, that adds up to roughly 0.03% of the Sun's total mass.
Because it is gigantic. The Sun is 333,000 times more massive than Earth. Even losing 4.26 million tonnes per second, it has spent only 0.03% of itself in 4.5 billion years. It has enough hydrogen for another 5 billion years.
In about 5 billion years, the Sun runs out of hydrogen in its core. It swells into a red giant, swallows the inner planets, then sheds its outer layers and collapses into a white dwarf the size of Earth. The furnace closes. The light goes out.