A red dwarf is a star that has a mass of less than half that of the Sun and a luminosity of less than one tenth. These stars are by far the most abundant type of star in the Milky Way, making up about three quarters of all stars in our galaxy. Red dwarfs are very long-lived, with some estimates suggesting they can burn for trillions of years. This makes them ideal candidates for hosting habitable planets, as any life on these worlds would have ample time to evolve.
Interestingly, red dwarfs may not always be red. When they first form, they are actually blue-white in color. As they age and their hydrogen fuel starts to run low, they cool down and redden. This transition can take billions of years, meaning that a planet orbiting a red dwarf might experience drastic changes in its climate over the course of its history.
Despite their small size and dim light, red dwarfs are actually quite active stars. They often flare brightly as magnetic activity causes hot plasma to rise up from their surface. This can make them dangerous places to live, as a strong flare could potentially strip away an atmosphere or bake a planet’s surface. However, there is evidence that many red dwarfs settle down after a few billion years and become much more stable.
There are many intriguing questions still to be answered about red dwarfs. For example, we don’t yet know how common Earth-like planets around these stars might be. With further study, we may find that these humble objects hold the key to understanding the habitability of our own Solar System and beyond.