In 1859, a British astronomer saw a bright flash on the Sun. It was a huge explosion called a solar flare. The next day, a very strong storm hit Earth's magnetic field.

People saw colorful lights in the sky, called auroras, even in Hawaii. Telegraph lines made sparks. Today we use much more electricity, so a storm like this could cause bigger problems.

On September 1, 1859, the British astronomer Richard Carrington was drawing sunspots when he saw two bright white lights appear on the Sun. This was the first solar flare ever recorded. The next day, the strongest geomagnetic storm in modern records hit Earth. Auroras, which are usually seen only near the poles, appeared as far south as Hawaii and Panama. Telegraph lines also had problems: some gave off sparks, and some could even send messages after their batteries were disconnected.

Today, a similar storm could damage power grids and satellites. In 1989, a much smaller storm caused a nine-hour blackout in Quebec, Canada. One study estimated a 12 percent chance of a Carrington-level storm within ten years.

On September 1, 1859, while sketching sunspots, the British astronomer Richard Carrington saw two brilliant white patches flare on the Sun for about five minutes, the first solar flare ever recorded. The next day, the most intense geomagnetic storm of modern times struck Earth. Auroras normally confined to high latitudes were seen in Hawaii and Panama, and telegraph systems malfunctioned, with lines sparking and some operating even after their batteries were disconnected. Re-evaluating historical records in 2013, two solar physicists estimated the flare at roughly X45, larger than any measured in the modern era, though such reconstructions carry considerable uncertainty.

Modern society is far more vulnerable: in 1989 a much weaker storm triggered a nine-hour blackout in Quebec, and in 2022 a minor storm increased atmospheric drag enough to bring down up to 40 newly launched Starlink satellites. In 2012, one researcher calculated about a 12 percent probability of a Carrington-class storm within a decade, but this relied on extrapolating trends to rare extremes, a limitation he acknowledged. Tree rings from Japanese cedars, meanwhile, point to an even larger solar event around AD 774.