The most common stars possess about a tenth of the mass of the Sun. A good example is the nearest star, Proxima Centauri, located 4.25 light years away and having 0.12 solar masses. Three rocky planets were reported to orbit that star: Proxima b with about 1.3 Earth masses, Proxima c with roughly 7 Earth masses and Proxima d with roughly 0.3 Earth masses, adding up to 8.6 Earth masses. TRAPPIST-1, a dwarf star of 0.09 solar masses at a distance of 39.5 light years, was found to have 7 rocky planets with a total of 6.4 Earth masses. It is reasonable to imagine that gravitational interactions during the history of dwarf stars expelled a comparable amount of rocky material from their vicinity into interstellar space.
What Lies Beyond: Exploring Interstellar Space
The scale of things is hard to grasp. The distance from Earth to the Moon — some four hundred thousand kilometers — is the…