How We See the Beautiful, Violent Sun

The sun is one of the most studied objects in the history of science. The ancient Babylonians and Chinese tracked sunspots and solar eclipses, etching their observations into clay tablets; these records would outlast their civilizations. When the telescope arrived in the early 1600s, astronomers such as Galileo Galilei, Christoph Scheiner, and Johannes Fabricius turned these instruments toward this nearest star, projected the image onto paper, and saw dark blemishes drifting slowly across the solar surface.

In the 1800s, our ability to understand the sun’s composition launched a new era of solar science. Spectroscopy could split light emitted from objects into a kind of barcode that characterized elemental makeup. Armed with this method, Pierre Janssen and Norman Lockyer independently found lines in the sun’s spectrum that didn’t match any known element on Earth. Lockyer named it helium, after Helios, the Greek god of the sun. It would be another 27 years before Sir William Ramsay isolated and identified that element on our planet.

In the early 1900s, the pioneering American astrophysicist George Ellery Hale discovered that the sunspots that Galileo and others had traced weren’t blemishes but magnetic storms, regions of intense activity that waxed and waned on the 11-year solar cycle. The French astronomer Bernard Lyot built a coronagraph in 1930: a telescope with a disc at its center that blocked the sun’s blinding light, mimicking an eclipse on demand. For the first time, scientists could study the corona — the sun’s ghostly outer atmosphere — without waiting for the moon to cooperate.

From the 1950s on, the space age allowed scientists to create instruments that could escape the observational barriers of Earth. Satellites and probes began directly measuring the solar wind — the constant stream of charged particles the sun throws off in all directions — along with the violent phenomenon of coronal mass ejections, plasma founts that are some of the most energetic events in our solar neighborhood. Since 1995, the Solar and Heliospheric Observatory, a collaboration between NASA and the European Space Agency, has been on constant surveillance, and NASA’s Solar Dynamics Observatory joined the fold in 2010. The Parker Solar Probe first flew through the corona itself in 2021. Its pass in 2024 was the closest any human-made object has ever come to a star.

Observations and questions have continued to accumulate. Why is the corona hundreds of times hotter than the surface below it? What drives the solar cycle? How do the electromagnetic radiation bursts known as flares decide to erupt? The instruments keep improving, and the secrets they uncover continue to fascinate.