Sun
What is Sun?
Stars· Diameter 1,392,700 km · mass 333,000× Earth. Our star holds 99.86% of the solar system's mass. Hydrogen fusion converts 4 million tons of matter into light every second; that light takes 8 minutes 19 seconds to reach Earth.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where Sun is in your sky right now: https://nowsky.org/solar/sky?sel=sun — location and time set automatically, no login.
Stellar figures
| Diameter | 1,392,700 km |
|---|---|
| Mass | 333,000× Earth |
| Surface temp | 5,500 °C |
| Age | 4.6 Gyr |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Related events
Frequently asked
- How big is Sun?
- 1,392,700 km.
- What is the mass of Sun?
- 333,000× Earth.
- In one line, what is Sun?
- Stars — Our star holds 99.86% of the solar system's mass.
- Where is Sun in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
1,361 watts per square metre — the solar constant
One square metre facing the Sun at Earth's distance receives 1,361 watts. This is the solar constant, measured continuously from above the atmosphere by satellites since 1978. Over the eleven-year activity cycle it varies by only about 0.1 percent — and is slightly brighter at sunspot maximum, because the brightness of the surrounding faculae outweighs the darkness of the spots.
Multiply that number by the area of a sphere at Earth's orbit and the Sun's total output comes out at 3.8 × 10²⁶ W; divide by Einstein's equation and it becomes the four million tonnes of mass the Sun loses every second. Earth's share is one part in 2.2 billion. The solar constant is also an input to climate models, and these measurements confirmed that changes in the Sun's brightness have contributed little to warming since the industrial revolution.
The star in depth
The Sun holds 99.86% of the solar system's mass by itself — eight planets and millions of asteroids split the remaining 0.14%. The solar system is essentially "the Sun, plus debris". Its core fuses 600 million tonnes of hydrogen into helium every second; the 4-million-tonne difference streams away as energy. Earth intercepts just one 2.2-billionth of it, and that sliver drives all our weather and life.
The visible surface sits near 5,500 °C, yet the corona above it exceeds a million degrees — a long-standing paradox that the Parker Solar Probe is investigating from inside the corona itself. Sunspots are regions where magnetic fields choke convection, running ~1,500 °C cooler, waxing and waning on the ~11-year cycle.
Zoom into the Sun in the orbit view for a simplified look at its ~25-day rotation, spot groups and prominences; the size ladder sets its 109-Earth diameter against ours.
The Sun's future is already scheduled: in about five billion years its core hydrogen runs out, it swells into a red giant swallowing Mercury and Venus, sheds its outer layers as a planetary nebula, and cools as an Earth-sized white dwarf. Long before that it brightens steadily, putting Earth's oceans under evaporation pressure within a couple of billion years. At 4.6 billion years old, the Sun is exactly at midlife.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.