Solar Orbiter Spots Tiny 'Campfires' Dotting the Sun's Surface

ESA and NASA dropped the first images from Solar Orbiter today, and they’re the kind of pictures that make you look twice. Scattered across the surface of the Sun are tiny, ubiquitous flares that the mission team has started calling “campfires” — miniature versions of the big solar flares we can see from Earth, except millions to billions of times smaller.

Solar Orbiter launched back in February, a joint ESA-NASA mission designed to get closer to the Sun than any imaging mission before it, and to eventually give us our first real look at the solar poles. These first images come from a batch of instruments taken during commissioning, before the spacecraft even reached its closest approach to the Sun. If this is what the “before” pictures look like, I’m very curious what happens once it’s in a stable science orbit.

Why these tiny flares matter

The campfires themselves aren’t the headline — it’s what they might explain. One of the Sun’s oldest unsolved puzzles is why its outer atmosphere, the corona, runs hundreds of times hotter than the surface below it. That’s backwards from how heat normally works: you’d expect things to cool off as you move away from the source, not heat up.

David Berghmans, the principal investigator for the EUI instrument that captured these images, floated the idea that these small-scale flares could be “nanoflares” — a long-hypothesized mechanism where countless tiny energy releases across the Sun’s surface could add up to enough heat to explain the corona’s extreme temperature. It’s not a new theory, but actually seeing candidate events like this, in this kind of resolution, is a different thing than modeling them from a distance.

I want to be careful here: nobody’s declaring the coronal heating problem solved. These campfires are a first look, captured before the spacecraft is even at full working distance. Confirming whether they’re actually nanoflares, and whether there are enough of them doing enough work to heat the corona, is going to take a lot more data and a lot more analysis.

Still, there’s something satisfying about a mission delivering an actual visual candidate for a decades-old theoretical mechanism this early in its life. Solar Orbiter isn’t scheduled to get properly close to the Sun for a while yet, and it hasn’t started sending back polar imagery either. If the “before” shots are already producing results like this, the next few years of solar physics could get interesting fast.

For anyone who follows space missions mostly through launch headlines and then loses track of them for years, this is a good reminder to keep an eye on Solar Orbiter. First-image releases are usually calibration checks and PR moments — this one might actually be pointing at real physics.