The Sun is an ordinary star - a ball of hydrogen and helium plasma so massive that its core fuses hydrogen into helium, releasing the light that powers everything here. It holds 99.8% of the Solar System’s mass, and that mass is why everything else orbits it.
Open the 3D Solar SystemPlanets are not held up by anything - they are falling toward the Sun constantly. But they also move sideways so fast that they keep missing it. That endless sideways fall is what an orbit is.
| Diameter | 1,391,400 km |
| Mass | 1.989e+30 kg |
| Surface gravity | 274 m/s² |
| Density | 1.41 g/cm³ |
| Rotation period | 609.1 h |
| Axial tilt | 7.25° |
| Mean temperature | 5,505 °C |
| Known moons | 0 |
| Atmosphere | The corona - a 1,000,000 °C plasma halo far hotter than the 5,500 °C surface below it, streaming outward as the solar wind. |
| Composition | Hydrogen (~74% by mass) and helium (~24%) plasma; the core fuses hydrogen into helium at about 15,000,000 °C. |
How we know: Helioseismology - reading the Sun’s surface oscillations - has mapped these zones directly; the core’s fusion is confirmed by detected solar neutrinos.