What fuels the sun?

How the sun heats the Earth

We all know it: Without the sun's heat, the Earth would be uninhabitable. So how does it work? The sun fuses roughly 600 million tons of hydrogen every second, the energy from which bursts out into space—including toward our planet. Our atmosphere...

An overview of the sun, from its formation to its role in fueling and protecting life on Earth

With a surface gravity almost 28 times Earth's, the sun's mass exerts enough pressure to raise temperatures in its core above 15 million degrees Celsius (27 million degrees Fahrenheit) and enable nuclear fusion. These reactions produce the energy that sustains Earth's photosynthesis-dependent food chains, while the sun's magnetic field protects the solar system from cosmic ionizing radiation.

A breakdown of nuclear fusion and what is impeding this near-limitless clean-energy resource

While today's nuclear reactors rely on fission, which releases energy by splitting heavy atoms, nuclear fusion releases energy by combining atoms together to form more massive ones. Fusion involves overcoming repulsive forces between the centers, or nuclei, of atoms, and, as of 2026, overcoming this repulsion takes more energy than is produced.

Fusion reactions and radioactive decay produce elements inside stars

Hydrogen, present since the early universe, serves as fuel for the proton-proton chain, producing helium, which is then incorporated into the CNO cycle to produce carbon, nitrogen, and oxygen. Additional fusions of helium with these elements and subsequent decays via the alpha ladder produce elements up to iron and bismuth.

What will happen and what will remain of the sun when it dies

Upon exhausting the hydrogen fuel in its core, gravitational pressure will collapse and heat up, causing a surrounding layer to become hot enough to fuse hydrogen and release energy that swells the outer layers. This will turn the sun into a red giant that will engulf Mercury, Venus, and (likely) the Earth. These outer layers will eventually be shed, leaving behind a white dwarf.

Visualize what happens to atoms during nuclear fission and how the process produces energy

Nuclear fission occurs when an unstable, often massive, atomic nucleus splits into smaller ones—daughter atoms—and releases energy. Within a nuclear reactor, these daughter atoms can collide and combine with neighboring atoms, destabilizing them and triggering a chain reaction of atomic splitting.

View a step-by-step breakdown of how helium is forged in stars alongside antimatter

During the proton-proton chain, four hydrogen nuclei—protons—are fused together to create an alpha particle—a helium nucleus—and produce the energy that supports a star's own weight. Through radioactive decay, two of these protons become neutrons, with each releasing an antielectron, or positron, and an electron neutrino.

View the internal structure of the sun and its puzzling surrounding atmosphere

From the stellar core to the surface, the sun's density decreases from more than 10 times that of lead to 0.00001% that of air, while temperatures drop from millions to thousands. Temperatures increase from the sun's surface to the outermost layer of its atmosphere—the corona—a phenomenon whose explanation is still under investigation.

The formation of a neutron star through a core collapse lasts one-tenth of a second

Massive stars keep fusing heavier and heavier elements in their cores to produce energy that pushes against the weight of the star itself. However, the fusion of silicon into iron consumes energy and initiates a feedback loop that rapidly compresses the stellar core, creating neutrons and neutrinos from the combination of electrons and protons.

Earth is the only planet in our solar system with fire

And while the sun seems like fire, and other planets have volcanoes, the sun and lava aren't the same thing as fire. To produce fire, a planet needs three ingredients: oxygen, fuel, and heat. No other planet has all three.

Solar power is converting the sun's energy into thermal or electrical energy

Solar energy is the most abundant renewable energy resource. It can be captured in photovoltaic cells to generate electricity, solar heating and cooling technologies for temperature control, and concentrated solar power to drive steam turbines.

The sun emits a continuous stream of plasma known as the solar wind

Composed of charged particles—electrons and ions—the solar wind is deflected around the Earth by the planet's magnetic field. More powerful solar storms, known as coronal mass ejections, are short-lived but produce huge clouds of plasma that disrupt technology upon reaching Earth.

A laser energy system has allowed scientists to achieve fusion ignition

In 2022, scientists used lasers to create a powerful implosion that bound hydrogen isotopes together, releasing more energy than was input into the system. Research is ongoing to achieve this self-sustaining reaction with larger yields and energy gains.

Heat slowly moves through Earth's mantle like softened wax

Energy trapped during Earth's formation and released via the radioactivity of elements is carried by convection currents towards the surface, while cooler, denser material sinks. The planet's core is almost as hot as the sun's surface.

Learn about solar neutrinos—about 70 billion of which pass through your thumbnail every second

About 100 quadrillion sextillion (10³⁸) of these elusive particles are created in the core every second, making up about 1% of the sun's total energy output. Because they seldom interact with normal matter, highly specialized equipment is needed to detect them, allowing scientists to probe what is happening in the solar core.

Breaking down sunlight and why the sun appears yellow despite emitting green light the most

This peak intensity is produced alongside a spectrum of other colors, which, when combined, make the sun appear white in space. Since Earth's atmosphere scatters bluer and greener wavelengths of light more than red and orange wavelengths, sunlight reaching Earth's surface appears yellow, while the sky appears blue. (Some readers may experience a paywall.)

Learn about photoautotrophs, the photosynthetic organisms at the base of the food web

The sun is the ultimate source of energy for the planet, but consumers along food chains, such as herbivores and carnivores, cannot harness this energy themselves and instead rely on consuming plants and other organisms that capture it to build carbohydrates. Besides plants, photoautotrophs include algae and some bacteria that convert solar energy into chemical energy for the biosphere.

Why it takes tens of thousands of years for light from the sun's core to reach its surface

Photons take about eight minutes to travel through empty space to Earth after leaving the sun's surface. However, traveling from the core to the surface involves these particles of light undergoing a random walk—scattering off charged particles deep in the sun like a pinball—causing a trip that is more than 200 times shorter to last as long as 170,000 years.

How its uneven rotation produces the sun's 11-year cycle and flips its magnetic poles

While charged material rises and falls in the sun's convection zone, which induces magnetic fields, different latitudes rotate at different rates, making these fields increasingly turbulent. This builds to a critical point—the solar maximum—where magnetic field-driven events, such as solar flares, become more common before the field collapses and flips, restarting the cycle.

How solar systems form

Learn how our sun, the planets, and other solar system bodies came to be with these videos and an infographic from NASA. Use this resource to visualize how the solar system formed and to model and describe the process.

Enough sunlight hits Earth in just 90 minutes to power the planet for an entire year

Despite this, in 2023, only 5.1% of electricity in the US came from solar energy. Solar panel technology has nonetheless made significant advancements since the 19th century, largely due to NASA's efforts in the space race.

Why Earth's atmosphere constantly loses the universe's lightest elements to space

The masses of hydrogen and helium are too small for these gases to be held by Earth's gravitational force, particularly when these atoms are given energy from collisions with high-speed particles from the sun. Although the planet loses a meter-wide balloon's worth of hydrogen every second, it will still take billions of years to exhaust the planet of this element.

The sun is not as exceptional as once believed, but it remains rarer than most stars

Once believed to be the center of the universe, the sun is a G-class star, the same category to which about 6% of the Milky Way's stars belong. However, the sun is younger than 85%, more massive than 95%, and more metal-rich than about 93% of all stars. Unlike the sun, half of all stars also exist in multi-star systems.

Antimatter engines would have the greatest energy output of all machines

These devices would annihilate matter with antimatter, converting mass into pure energy. A teacup of fuel would release energy equivalent to that of a hydrogen bomb, but stabilizing and storing that much antimatter remains a challenging task. Alternatively, hybrid systems would utilize small amounts of antimatter to initiate nuclear reactions.

Learn how your body is, scientifically, like a firework with its own slow, controlled burn

This NPR video makes clear that there are surprising similarities between how our bodies and fireworks function. Fireworks and our bodies are both packed with carbon atoms, and have controlled releases of energy that create heat—keeping the human body warm or fueling fireworks' heat, respectively. What's more, the human body even emits a tiny bit of light somewhat similar to fireworks—though it's not visible to the human eye.

A composite of telescope images of the sun, which each reveal unique solar features

While traditional cameras can reveal sunspots—cooler regions on the sun's surface—in visible light, x-ray detectors can highlight explosions of high-energy plasma and magnetic fields known as coronal mass ejections. Hydrogen-alpha filters can reveal clouds and filaments of material suspended in magnetic fields above the sun's surface.

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

How big is a supernova explosion?

Supernovas are the biggest explosions in the universe, often obliterating the area surrounding them. So what would happen if one exploded near Earth? If the sun went supernova it'd be like getting hit by a nuclear explosion every second for weeks. Of course, that's not happening anytime soon. This animated video shows how distance is the key factor, and how you shouldn't be worried.

The lifetime of a star is determined by its initial mass

More massive stars burn through their fuel at ever-increasing rates, causing them to have shorter lifetimes than less massive stars, despite starting with more hydrogen to fuse. In clusters of stars that likely formed together, observing what mass stars are no longer fusing hydrogen estimates the age of the cluster.

Coronal mass ejections and solar flares produce the most extensive auroras

The most intense geomagnetic storms are produced when massive clouds of plasma—ionized gas—are expelled from the sun's upper atmosphere and interact with the Earth's magnetic field. These storms expand where auroras are bright enough to be seen to regions farther from the poles, particularly during peak periods of the sun's 11-year intensity cycle.

The continuous decay of radioactive elements regenerates geothermal energy reserves

Geothermal power is a renewable energy source derived from Earth's interior, where the core reaches temperatures exceeding 5,000 degrees Celsius (9,000 degrees Fahrenheit). These temperatures result from leftover energy from collisions during planetary formation, with radioactive decay in the core releasing additional energy that travels to the surface.

The history of helioseismology, which studies seismic waves traveling within the sun

Following World War II, scientists began studying the sun's influence on radio waves, the most popular form of mass communication at the time. NASA missions to study the sun's interior have since helped develop explanations for various phenomena in its atmosphere and protect digital infrastructure.

Why did the Big Bang produce something, rather than nothing?

One of the more remarkable things—among many remarkable things—about the big bang is how matter seemingly won out over antimatter. Int that initial moment of creation and annihilation, it turns out, neutrinos may well have pushed the universe toward forming matter over antimatter. This New York Times article delves deeply, asking several scientists for their input.

Uranium's ability to split easily makes it the most common catalyst for nuclear power

Uranium is commonly found in rocks, water, and soil worldwide, but significant industrial processes are needed to process and enrich it for efficient reactor usage. After being irradiated in reactors, it must be cooled down before disposal.

The dynamo theory explains how planets generate their own magnetic fields

According to the theory, a large magnetic field generator, or dynamo, is created when liquid metal flows through the planet's outer core, producing electric currents that generate a magnetic field. Magnetization patterns in rocks on the surface of planets can serve as evidence for the presence of this internal structure at some point in the celestial object's past.

Rubisco, the crucial enzyme powering photosynthesis

Photosynthesis is the crucial process by which plants absorb sunlight, take up water, and breathe in carbon dioxide, prompting chemical reactions that result in the byproducts sugar and oxygen. A key enzyme, rubisco, is responsible for it all, but it is inefficient. This video explores the key protein and reveals fascinating facts about oxygen and photosynthesis.

Concentrated sound waves can collapse microscopic bubbles, creating light

The phenomenon, known as sonoluminescence, can generate extremely short, high-intensity flashes from the sudden focusing of sound energy, which can drive the temperature within the bubbles to values over twice that of the sun's surface.

Artificial photosynthesis turns CO₂ into sustainable fuel

Carbon conversion focuses on a central perplexing question: if carbon dioxide is a leading driver of climate change, and fossil fuels are made of carbon-based molecules, can we devise a way to convert CO₂ into useful alternatives efficiently? This video breaks down a potential pathway using artificial photosynthesis, which uses sunlight to convert CO₂ into fuel.

Find out how much energy in the US comes from renewable sources and other FAQs

Browse frequently asked questions about renewables, from the amount of energy production by state to the cost of electricity generation by power source.

The H-bomb is hundreds of times more powerful than the bomb dropped on Hiroshima

Unlike the atomic bombs dropped on Hiroshima, which relied on nuclear fission, the hydrogen bomb uses fusion to unleash vastly greater destructive power. Developed by both superpowers in the 1950s, it gave each the ability to destroy entire cities in seconds.

Everything you need to know about Jupiter, the gas giant

NASA introduces you to the fifth planet from the sun, the gas giant Jupiter. When it comes to our solar system, Jupiter is the biggest kid on the block. Named after the king of the Ancient Roman gods, Jupiter is a planet of storms and chaos, most famously in its Great Red Spot, a hurricane larger than the earth itself.

How does your body turn food into energy?

Cells get energy via a process known as cellular respiration, which involves turning glucose into ATP or adenosine triphosphate. Breaking the phosphate bonds of ATP results in usable energy being released into cells, which can then use that energy to power biological processes. This 10-minute video explains how glucose turns into ATP, giving the body the energy it needs to survive.

Hubble's average used power is less than half the power generated by its solar arrays

The space telescope's components use about 2,100 watts, or about as much power as five refrigerators. When exposed to sunlight, the solar arrays can generate over 5,200 watts for the observatory, which was engineered by a team that included Judith Love Cohen, mother of actor Jack Black.

Learn how helium is used in the US, the world's largest producer of the noble gas

About 44% of the global supply comes from the US, as much as the next two biggest producers—Qatar and Russia—combined. According to the US Geological Survey, more than half of this helium is used in scientific and engineering equipment (22%), non-welding-related manufacturing and fabrication (17%), and as a lifting agent (17%).

Early Earth lifeforms likely made energy via mineral reactions, not sunlight

Earth's initial atmosphere was filled with carbon dioxide, methane, and water, with most oxygen locked away in the rocky crust. Over time, bacteria evolved to slowly release that oxygen into the atmosphere by breaking down rock.

Data suggests fossil fuels are the dirtiest and most dangerous energy sources

Although all energy sources have trade-offs, fossil fuels emit the most greenhouse gases per unit of energy and have the highest rate of accidents. Low-carbon energy sources—including nuclear power—have the lowest death rates and fewest adverse climatic effects.

Solar sails use light as a means of propulsion

Photons possess momentum and can transfer it to objects they strike or bounce off, imparting radiative pressure, or a light-based force over a small surface area. Lasers fired at observational equipment with specially designed sails can theoretically use this mechanism to accelerate up to 20% the speed of light.

Dark matter and dark energy make up 95% of the universe

Dark matter holds galaxies and other large-scale structures together through gravity, and dark energy drives the universe's accelerating expansion. While scientists do not know what either is made of, they see how these dark components affect the normal matter in the universe.

The basic science of rockets

How do rockets work? What is the science behind a rocket launch? How does a rocket go into space? In this short and simple video, we discuss the science of rocket propulsion and what takes to get these vehicles into orbit.

How helium turns the Large Hadron Collider into the world's largest cryogenic system

Across three stages, five "cryogenic islands," and weeks of cooling, 36,000 metric tons of magnets are successively brought down to temperatures colder than outer space using a closed liquid helium system. Helium continues to circulate during the collider's operation to maintain the magnets' temperature and the transmission of electrical current with zero resistance.