WHAT NASA AND NOAA SAY

Our nearest
star.

The Sun is an ordinary star, seen up close.

The Sun rising low and golden over misty farmland, with soft layered hills and a pale clear sky — AI-generated image, not a photograph of a real person or place.

A yellow dwarf star
Powered by fusion
Busy every 11 years
4.5 billion years and counting

It is a ball of hydrogen and helium held together by its own gravity, about 150 million kilometres away. Deep inside, hydrogen fuses into helium, and that powers every sunrise.

Updated 14 October 2026

THE SHORT ANSWER

A middle-sized star,
a lively one.

Big by our standards, average for a star.
Its activity rises and falls in a cycle.

STAR

An average-sized star

NASA calls the Sun a yellow dwarf, about 100 times wider than Earth, yet only an average star in terms of its size.

See the numbers

SPOTS

Cooler, darker patches

Sunspots are cooler areas on the visible surface, where intense magnetic fields push up from inside the Sun.

Compare the layers

CYCLE

An 11-year rhythm

Sunspot numbers rise and fall over about 11 years. NASA and NOAA said in October 2024 that the Sun had reached solar maximum.

How the cycle works

A QUICK TOUR OF THE SUN

How hot is
each part?

Pick a part of the Sun to see its temperature. The bar shows how hot it is compared with the other parts.

Figures from NASA's Sun facts page and NOAA's Space Weather Prediction Center. All are approximate.

Sun layers

Choose a part of the SunThe coreThe convection zoneThe visible surfaceA sunspotThe corona

The core≈ 15 million °C

The hottest part, where hydrogen is fused to form helium. Those nuclear reactions power the Sun's heat and light.

The convection zoneBelow 2 million °C

Here hot plasma bubbles up towards the surface, carrying energy outwards like a pan of simmering water.

The visible surface≈ 5,500 °C

The photosphere is the layer we see. It is about 250 miles thick, and the Sun has no solid surface at all.

A sunspot≈ 7,000 °F

NOAA puts a sunspot's centre at about 7,000°F, against about 10,000°F for the photosphere around it, which is why spots look dark.

The coronaUp to 2 million °C

The outer atmosphere is far hotter than the surface below it. NASA calls this one of the Sun's biggest mysteries.

Sources: NASA Science, Sun facts; NOAA Space Weather Prediction Center, Sunspots and the solar cycle.

TWO NUMBERS WORTH KNOWING

Huge, and
a long way off.

One figure on the Sun's size,
one on how far its light travels.

1.3 million

Earths it would take to fill the Sun

NASA says the Sun is about 1.4 million kilometres across and holds 99.8 percent of the mass of the solar system.

SIZE · NASA

8 min 20 s

Time for sunlight to reach Earth

Light crosses the average Sun-Earth distance of about 150 million kilometres in about 8 minutes and 20 seconds, says the Smithsonian's Air and Space Museum.

DISTANCE · SMITHSONIAN

That light is the end of a much longer trip. NASA says energy from the core bounces around in the Sun's radiative zone for about 170,000 years before it reaches the convection zone.

Green and pink aurora glowing over a still Scottish loch at night, reflected in the water below a dark mountain — AI-generated image, not a photograph of a real person or place.

HOW THE SOLAR CYCLE WORKS

Quiet, busy,
quiet again.

The Sun's magnetic activity rises and falls in a cycle of roughly 11 years. Scientists track it by counting sunspots.

Solar minimum
The lull of the cycle, when few sunspots appear. Cycle 24 ended and Cycle 25 began in December 2019.
New spots appear
A new cycle starts when sunspot groups show up at higher latitudes with magnetic polarity opposite to the last cycle's.
Solar maximum
The most active part of the cycle. NASA and NOAA announced on 15 October 2024 that Cycle 25 had reached it.
The poles flip
Roughly every 11 years, at the height of the cycle, the Sun's magnetic poles swap places, and the count begins again.

A STAR WITH A LIFE STORY

Halfway through
its life.

NASA says the Sun is about 4.5 billion years old and a little less than halfway through its lifetime. It turns about once every 25 Earth days at its equator and 36 at its poles, because it is gas, not solid rock.

In about 5 billion years it is expected to swell into a red giant, which may engulf Mercury, Venus and possibly Earth, before ending as a white dwarf.

A white card on a garden table showing a projected image of the Sun's disc with a few small dark sunspots, cast by a small telescope — AI-generated image, not a photograph of a real person or place.

Questions

Questions people ask

What kind of star is the Sun?

NASA classes the Sun as a G2 V yellow dwarf, a main-sequence star. It is a ball of hydrogen and helium held together by its own gravity and is only an average star in terms of size.

How far away is the Sun?

About 150 million kilometres (93 million miles) on average. At that distance sunlight takes about 8 minutes and 20 seconds to reach Earth.

How does the Sun make light?

In the core, at about 15 million °C, hydrogen is fused to form helium. NASA says these nuclear reactions power the Sun's heat and light.

What are sunspots?

Dark areas on the visible surface where intense magnetic fields push up from inside. They are cooler than the surroundings, last from days to months, and range from about 1,600 to 160,900 kilometres across.

How long is the solar cycle?

About 11 years. NOAA numbers the cycles from Solar Cycle 1 in 1755. The current one, Cycle 25, began in December 2019 and reached solar maximum, announced in October 2024.

Our nearest
star.