Sun

Star

The Sun is the star at the centre of the Solar System — a nearly perfect sphere of hot plasma that holds 99.86% of the system's mass and supplies, through nuclear fusion in its core, essentially all the energy that drives the planets, weather and life.

Open in 3D viewSee Sun in the live, interactive 3D map

Key facts

Mass

1.99 × 10³⁰ kg

1 M☉

Radius

695,700 km

109× wider than Earth

Surface temperature

5,772 K (5499 °C)

Luminosity

3.83 × 10²⁶ W

Spectral type

G2V (yellow dwarf)

Science

Physical

Mass: 1.99 × 10³⁰ kg · 1 M☉
Radius: 695,700 km · 109× wider than Earth
Density: 1,410 kg/m³ · 1.4× water
Spectral type: G2V (yellow dwarf)

Rotation

Equatorial period: 25.0 days
Note: Differential rotation: ~25 days at the equator, ~35 days near the poles

Composition

By mass: ~73.5% hydrogen, 24.9% helium and 1.6% heavier elements, by mass

Magnetism & activity

Surface field: 1 gauss
Activity cycle: 11 years

Temperature

Surface: 5,772 K (5499 °C)
Core: 15,700,000 K (15699727 °C)

Radiation & temperature

Luminosity: 3.83 × 10²⁶ W · 1 L☉
Absolute bolometric magnitude: 4.74
Surface temperature: 5,772 K (5499 °C)
Peak wavelength: 502 nm · green-yellow visible light
Surface magnetic field: 100 µT

Discovery & history

First known: Known since antiquity
Name: Old English 'sunne'; Latin 'Sol', Greek 'Helios' — names as old as language itself.

The Sun has been known and worshipped for as long as humans have existed; it needed no discovery. Ancient cultures tracked its yearly path to build calendars and aligned monuments such as Stonehenge to its solstices. Only in recent centuries did we learn what it is: Galileo's telescope revealed sunspots in 1610, spectroscopy in the 19th century showed it is made of hydrogen and helium, and in the 1920s–30s physicists realised it shines by nuclear fusion in its core.

1994UlyssesObserved from afar
First spacecraft to fly over the Sun's poles, sampling the solar wind out of the ecliptic plane.

Images

The Sun today — Corona — AIA 193 Å — NASA/SDO · NASA SDO

The Sun today — Chromosphere — AIA 304 Å — NASA/SDO · NASA SDO

The Sun today — Coronal loops — AIA 171 Å — NASA/SDO · NASA SDO

The Sun today — Active regions — AIA 211 Å — NASA/SDO · NASA SDO

The Sun today — Visible surface — HMI — NASA/SDO · NASA SDO

The Sun today — Magnetogram — HMI — NASA/SDO · NASA SDO

Solar Dynamics Observatory Artist Concept — NASA/GFSC · NASA Image Library

SDO Transit, September 2015 — NASA/GSFC/Solar Dynamics Observatory · NASA Image Library

Images from open archives · credit shown per image