More often than not, astronomers have a specific something they’re looking for when searching the cosmos. But the universe is achingly huge and mysterious, leading to discoveries no one ever set out to find.
These unexpected catches often end up being way cooler and more significant than what astronomers intended to explore. Here are ten of our favorite “accidental” cosmic discoveries—unintentional findings that nevertheless contributed greatly to our understanding of the universe.
1. Uranus (1781)
In the spring of 1781, British astronomer William Herschel found a faint, sluggish object in the constellation Gemini. At first, Herschel, who was cataloguing stars at the time, was convinced that the object was a comet. Follow-up observations revealed that it had moved across the sky, and apparent comet-like features were visible. Later, Finnish-Swedish astronomer Anders Johan calculated the orbit of Herschel’s discovery, which strongly suggested that this was a planet, later named Uranus, and not a comet.
2. Ceres, the first asteroid…uh, dwarf planet (1801)
Similarly, Italian astronomer Giuseppe Piazzi was trying to create an accurate map of star positions when he noticed a strange outlier “star” that kept moving across the sky. Piazzi also thought he was looking at a comet, but subsequent observations hinted that the object was a new planet orbiting the space between Mars and Jupiter.
Further analysis stripped Ceres of its planetary status, and for a long time, it was considered the first asteroid ever discovered. Then, during the great purge of Pluto in 2006, Ceres was reclassified as a dwarf planet.
3. Solar flares (1859)
In 1859, British astronomer Richard Carrington inadvertently documented what would become known as the Carrington Event. He was studying sunspots at the time and had his telescope pointed at our host star when he witnessed a sudden, intense flash of light, later identified as a solar flare. The flare led to the strongest geomagnetic storm ever detected on Earth and the discovery of an entirely new stellar phenomenon.
4. Cosmic X-rays (1962)
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