The Sun compared to Earth

Our star — almost all the material in the whole solar system, mostly hydrogen and helium.

How big is the Sun compared to Earth?

The Sun is roughly 109 times as wide as Earth.

The Sun turns round once in about 24 Earth days; Earth takes about 24 hours.

The Sun’s surface is 5,499 °C. Earth runs from −89.2 to 56.7 °C.

The Sun makes up 99.8% of the total mass of the solar system.

What it is like: By mass it is about 73% hydrogen and 25% helium. Core temperature 15.71 million °C.; How we know: Nobody has ever gone near the Sun’s core — scientists split sunlight into a rainbow spectrum and read the dark lines different elements leave behind, like a chemical fingerprint. The core temperature comes from physics models of nuclear fusion, checked against the way the whole Sun rings: its surface rises and falls in waves about five minutes long, and their pitch depends on what is inside (helioseismology).
Rotation: Differential rotation: 24.47 days at the equator (Snodgrass & Ulrich 1990), slowing to 34.19 days at the poles. The often-quoted 25.38 days — 27.28 as seen from the moving Earth — is Carrington’s, the rate of sunspots at middle latitudes.; How we know: Tracked by watching sunspots and other surface features drift at different speeds depending on latitude, and confirmed by Doppler-shift measurements of the surface plasma itself.
Looking at it: Never look at it directly, or through binoculars or a telescope, without a proper solar filter over the front.

The numbers

Across	1.391 million km
One spin	24.47 days at its equator, longer towards the poles
Surface temperature	5,499 °C