Parker Solar Probe is moving fast enough to travel from London to Paris in two seconds, and the scientists who built it hate that. The Sun sitting at the center of our solar system has been overhead every single day of human history, and it turns out almost everything most people picture when they look up is wrong. Right now, a generation of solar scientists is rewriting the textbooks, using spacecraft, ground telescopes, and a technique so improbable it involves listening to music the Sun plays on itself. Cleo Abram takes us on a full deep dive.
We are already inside the Sun and always have been
Before any probe even leaves Earth’s neighborhood, the first surprise lands hard. The Sun’s outer atmosphere, called the heliosphere, extends roughly 100 times farther than the distance between Earth and the Sun, swallowing our entire planet in the process. ‘We are living not just with a star, but living in a star’s atmosphere, which is pretty cool,’ said the head of heliophysics at NASA, the person responsible for all of the agency’s solar research.
Getting a spacecraft anywhere near the actual solar surface is a logistical nightmare. Earth is moving sideways relative to the Sun so fast that canceling that motion requires more energy than escaping the solar system entirely. That is why it took the Parker Solar Probe more than six years of spiraling inward before it crossed into the corona in 2021, the Sun’s inner atmosphere visible during a solar eclipse. When Parker finally crossed that threshold, it was still about nine times farther from the Sun than the Sun’s own diameter. The scientists who built it wish it moved slower. ‘I want Parker to spend as much time as possible very close to the Sun so we can get all the wealth of the data,’ one of its researchers said plainly.
Inside the corona, Parker recorded something no one expected: sounds. Chirping, hissing, and whooshing converted from electric and magnetic waves into audio. The pitch rises when the corona gets hotter. When a solar storm erupts, everything gets louder.
Those storms matter far beyond any aesthetic curiosity. In 1967, a massive solar event jammed US military radars in northern Greenland. ‘They thought the Soviets had jammed,’ the NASA heliophysics chief explained. ‘Fortunately, the US Air Force already had a solar physics group which could quickly say, no, no, no, put the planes back on standby.’ With future moon bases and Mars missions offering no magnetic field to hide behind, understanding the Sun’s 11-year activity cycle is now a matter of human survival. ‘I want to be able to tell them, you can go on Expedition X for this many hours, days, and be able to say with confidence that they’re going to be able to do that without risking their lives.’
Light that left the Sun’s core before humans wore clothes
Below the corona, the Sun’s surface, called the photosphere, runs at 5,500 degrees Celsius, hot enough to boil diamonds. The newest and most powerful solar ground telescope in the world has now captured the most detailed close-ups ever taken of that surface. Each churning bubble of plasma visible in those images is the size of France. A sunspot, darker and cooler than the surrounding plasma, stretches wider than the entire Earth. In 1795, the astronomer Sir William Herschel proposed in a published paper that sunspots might be openings revealing a solid, inhabited surface below. No Sun people were found.
Deep inside the Sun, past the convective zone, sits the radiative zone, where plasma is so dense that a photon of light bounces around like a pinball on average for 170,000 years before escaping. The energy warming a person’s face on a Tuesday afternoon has been traveling since before modern humans existed.
Scientists map the Sun’s interior without any probe ever reaching it by studying the pressure waves the boiling outer layers send through the star, the same logic used to study Earth’s interior through earthquakes. ‘The Sun is a musical instrument that plays many, many notes,’ said the researcher who uses this technique, called helioseismology. At the very core, pressure reaches the equivalent of 250 billion Earth atmospheres, and 600 million metric tons of hydrogen fuse into helium every second. And yet, per cubic meter, the Sun’s energy output is roughly similar to a lizard’s metabolism. The human body, pound for pound, generates more energy than the core of the Sun.
A question the head of heliophysics at NASA cannot answer
The 11-year solar activity cycle that determines when solar storms peak and when they quiet is one of the Sun’s defining rhythms, and no one knows why it exists. ‘Nobody knows or understands why that is,’ the head of heliophysics at NASA said without hesitation.
The Sun is 4.5 billion years old, middle-aged by stellar standards, and will eventually expand into a red giant large enough to engulf Mercury, Venus, and possibly Earth. For now, Parker keeps making passes, and the Solar Dynamics Observatory keeps snapping images across multiple wavelengths, described by NASA as ‘the beating heart of watching the Sun every day.’ The next time a photon from an 8-minute-and-20-second journey across 150 million kilometers lands on someone’s skin, that energy started moving before the first human being pulled on a piece of clothing.
