Astronomers are interested in red dwarfs and their orbiting planets. According to some studies, up to 85% of stars in the Milky Way may be red dwarfs, and 40% of these may contain Earth-like exoplanets in their habitable zones. But there are some issues with their potential habitability. One such problem is tide blocking.

Red dwarf stars are sometimes called “M dwarfs,” although the terms can be somewhat vague. The confusion between the terms red dwarf and M dwarf arises because of temperature and mass. One definition of a red dwarf is synonymous with an M dwarf, based on a maximum temperature of 3900 K and a maximum mass of 0.6 solar masses.

Other definition of red dwarf is hotter stars with a maximum temperature of 5200 K and a maximum mass of 0.8 solar masses. This definition includes all K-type main sequence stars, also called K-dwarfs. Another definition of red dwarf includes only part of the K-dwarf classification, while another includes some brown dwarfs.

In general, red dwarfs are the smallest and coolest main sequence stars. Because they are low-mass objects, they develop slowly and live for a long time. Their smallest masses can maintain a stable brightness for trillions of years, but there are no such old red dwarfs in the universe yet.

No matter how astronomers define them, there are a lot of them. If the estimate of 250 billion stars in the Milky Way is correct, 212 billion of them may be red dwarfs. Astronomers believe that the population of red dwarf stars contains many rocky planets in their habitable zones. That’s why the astronomical community has gone to great lengths to study red dwarfs: They’re like a cookie jar of a Milky Way exoplanet.

Red dwarfs are small and faint. Other stars can be so bright that it is almost impossible to detect minor planets passing in front of them. But red dwarfs are much less bright, so their light doesn’t create the same interference. The same dimness makes them difficult to observe from long distances, but astronomers have devised ways to circumvent these limitations. The European Southern Observatory (ESO) is running a project called SPECULOOS, the search for habitable planets that outshine extremely cold stars. SPECULOOS is a system of four robotic cameras at the Paranal Observatory. Source