Messier 40 - Winnecke 4

Many people dislike this Messier object, but I actually think it is a rather amusing one. Often referred to as Messier’s small mistake, it is better known as Winnecke 4. To this day, we are not entirely sure why Charles Messier decided to include it in his catalog of objects that could potentially be mistaken for comets. Perhaps he believed it was a true double star system. However, even that turned out not to be correct. For a long time Winnecke 4 was classified as a double star, meaning two stars that appear very close together in the sky. But in 2002 astronomers suggested that it might actually be an optical double, two unrelated stars that only appear close together from our line of sight. This suspicion was confirmed in 2016 using precise data from the Gaia space telescope. The measurements showed that the two stars are at different distances and are not gravitationally bound to each other. In other words, they are not a true binary system, just a chance alignment.

Despite its somewhat mistaken identity, I honestly think it is charming that this object remains part of the Messier catalog. It adds a human touch to the history of astronomy. It is a reminder that even experienced observers like Messier could make small errors. For me, as an astrophotographer working toward completing the entire catalog, it is a relatively easy object to capture and a fun story to share with others. Sometimes it is not just about spectacular nebulae or galaxies, but also about the history and quirks behind the objects we observe.