The Sun is the most familiar star in the sky, but there is much more to it than the light and heat we experience on Earth. It contains almost all the mass in the Solar System, carries Earth on a 230-million-year journey around the Milky Way, and can generate solar storms powerful enough to disrupt technology on Earth — one famously shocked telegraph operators and sent sparks flying from their equipment.
Even some of the most familiar things about the Sun are not quite what they seem. It isn’t really yellow, it has no solid surface, and the energy reaching Earth today began its journey deep inside the Sun more than 100,000 years ago. Here are ten fascinating facts about our nearest star.
1. The Sun Contains Almost All the Mass in the Solar System
The Sun contains about 99.8% of the mass in the Solar System. That leaves the eight planets, their moons, dwarf planets, asteroids, comets and everything else sharing just 0.2%.
This extraordinary imbalance dates back to the Solar System’s formation, when most of the material in the original cloud of gas and dust accumulated at the center to form the Sun.
The Sun is about 865,000 miles (1.4 million km) across, or roughly 109 times Earth’s diameter. Around 1.3 million Earths could fit inside the Sun by volume, but it would take only about 330,000 Earths to equal its mass. The difference is because the Sun’s material is, on average, much less densely packed than Earth’s rock and metal.
And here’s the twist: the Sun isn’t particularly large by stellar standards. Giant and supergiant stars can make our enormous Sun look positively small.
2. The Sun Isn’t Really Yellow
Despite its familiar appearance — and the fact that it’s commonly called a yellow dwarf — the Sun’s light is actually white. So why call it yellow? “Yellow dwarf” is a traditional term dating from when stars like the Sun were commonly described as yellow. The name has stuck, although astronomers more precisely classify the Sun as a G2V main-sequence star.
Sunlight looks white because it contains all the colors of the visible spectrum. When those different colors of light reach our eyes together, we perceive their combined light as white. So why does the Sun often look yellow from Earth? The culprit is our atmosphere. Tiny molecules in the air scatter blue light much more readily than red light — the same effect that makes the daytime sky appear blue. With some of that blue light scattered away, the remaining sunlight appears warmer, giving the Sun its familiar yellowish appearance.
At sunrise and sunset, the Sun is low on the horizon, so its light takes a much longer path through Earth’s atmosphere before reaching our eyes. Along that longer path, more blue light is scattered away, leaving more orange and red light to reach us directly. That’s why a white Sun can appear yellow, orange or even deep red from Earth.
3. The Sun Has No Solid Surface
The Sun may look like a solid glowing ball in the sky, but there is no solid surface beneath that bright disk. Instead, the Sun is an enormous sphere of plasma — superheated, electrically charged gas.
What we usually call its “surface” is the photosphere, the layer from which most of the visible sunlight we see escapes into space. Because the photosphere is opaque enough that we cannot see much deeper into the Sun, it creates the appearance of a distinct surface.
And you certainly couldn’t stand on it. If you could somehow survive the roughly 10,000°F (5,500°C) temperature, there would be no ground beneath your feet — you would simply continue downward into increasingly hot and dense solar material.
4. The Sun Doesn’t Rotate as One Object
How long is a day on the Sun? Surprisingly, there isn’t one simple answer. Because the Sun isn’t a solid object, different parts of it rotate at different speeds.
Near the equator, the Sun completes a rotation in about 25 Earth days, but this gradually slows toward the poles, where a rotation takes around 36 days.
This uneven rotation has much bigger consequences than simply making a solar “day” difficult to define. It helps twist and distort the Sun’s enormous magnetic field, storing energy that contributes to some of the explosive activity we see on its surface.
5. The Sun Flips Its Magnetic Poles
About every 11 years, something extraordinary happens to the Sun: its north and south magnetic poles switch places. Magnetic north becomes south and magnetic south becomes north.
It isn’t an overnight flip. As the Sun becomes more active, its magnetic field grows increasingly tangled and chaotic. Eventually, the old polar fields weaken and new ones emerge pointing in the opposite direction — almost as though the Sun has dismantled its magnetic field and rebuilt it backwards.
The reversal happens around the most active part of the solar cycle — the rise and fall in the Sun’s magnetic activity — when sunspots and powerful eruptions become much more common. After the cycle repeats, the poles reverse once more. That means it takes roughly 22 years — two flips — for the Sun’s magnetic field to return to the same overall orientation it started with.
6. A Solar Storm Once Disrupted Technology Across Earth
In 1859, an enormous eruption from the Sun struck Earth’s magnetic field, triggering the Carrington Event — the most intense geomagnetic storm ever recorded. Telegraph systems across North America and Europe went haywire, with sparks flying from equipment and operators receiving electric shocks. At the same time, spectacular auroras spread far beyond their usual polar skies and deep into the tropics, with some displays reportedly bright enough for people to read by in the middle of the night.
The technology has changed completely since 1859, but the vulnerability hasn’t gone away. A severe solar storm today could knock out satellites, GPS, radio communications and power grids rather than telegraph wires. It’s already happened on a smaller scale: in 1989, a considerably less extreme storm knocked out Quebec’s entire power grid, leaving around six million people without electricity for nine hours.
Modern monitoring gives us some warning, and grid operators can take protective steps when a storm is detected. But a storm on the scale of 1859, hitting a world this dependent on electronics, remains one of the more serious natural threats our technology-dependent civilization still hasn’t fully solved.
7. Today’s Sunshine Began Its Journey More Than 100,000 Years Ago
Energy produced deep in the Sun’s core has to fight its way through incredibly dense solar material, repeatedly interacting with matter before it can finally escape freely into space. Amazingly, the journey through the Sun can take well over 100,000 years. The bright “surface” we see is essentially the outermost layer from which that light can finally escape.
Once free of the Sun, however, everything changes. Light crosses the 93 million miles (150 million km) to Earth in just 8 minutes and 20 seconds. The sunshine warming your face today therefore carries energy that began working its way outward through the Sun long before recorded human history.
8. The Sun Takes Us on a 230-Million-Year Journey Around the Milky Way
The Sun may look fixed in the sky, but it is carrying the entire Solar System on an immense journey through the Milky Way. The Sun, Earth, the other planets and everything else orbiting our star are travelling together around the center of our galaxy.
One complete circuit takes roughly 230 million years. To put that into perspective, the last time the Solar System was in roughly this part of its galactic orbit, dinosaurs were only beginning to appear on Earth.
Since the Sun formed about 4.6 billion years ago, it has completed only around 20 trips around the Milky Way. Each one is sometimes called a galactic year — meaning the Sun is only about 20 galactic years old.
9. Earth Is Inside the Sun’s Vast Sphere of Influence
The Sun doesn’t end at the glowing disk we see in the sky. Material from its outer atmosphere is constantly streaming outward into space, creating the solar wind — a flow of charged particles that sweeps past Earth and continues far beyond the planets.
As this solar wind expands, it creates an enormous bubble around the Solar System called the heliosphere. Earth lies deep inside it, continually exposed to particles flowing from the Sun, although our planet isn’t defenseless: Earth’s magnetic field creates a protective magnetosphere that deflects much of this charged-particle flow around us.
From Earth, the solar wind continues outward for billions of miles and far beyond Pluto before finally meeting interstellar space. That boundary is so distant that only Voyager 1 and Voyager 2 have ever crossed it.
So in a sense, we don’t merely orbit the Sun — we live inside its heliosphere, a vast region of space created and shaped by the Sun itself.
10. The Sun Is Slowly Getting Brighter
The Sun may seem like the most constant thing in our sky, but it isn’t the same star it was when Earth formed. Over its lifetime, the Sun has gradually become brighter, and that process is still continuing.
As hydrogen is converted into helium in its core, conditions there slowly change, causing the Sun to produce more energy. Scientists estimate that the young Sun was only about 70% as bright as it is today — meaning Earth has spent billions of years orbiting a star that has been steadily turning up its output.
And the change isn’t finished. The Sun will continue growing brighter as it ages. Billions of years from now, it will leave its present stable phase altogether and swell into a red giant, becoming vastly brighter than it is today.
The Sun that rises tomorrow will look exactly the same to us — but on the timescale of planets, our seemingly unchanging star is changing all the time.