Why are there so many dwarf stars (red and white) among the nearest stars, but none among the brightest stars?
Answers
Nature likes to make many more smaller stars than massive ones. For every Sun like star there are dozens of red dwarfs out there, and a super massive star is something like one out of every million or ten million stars on average. When interstellar clouds are hit by shock waves from supernovae or collide with each other, gravity takes over and they start to contract and fragment into protostars. For some reason, the process of fragmentation and collapse of interstellar clouds favors smaller stars. Massive stars can only exist in star forming regions, with lifetimes as short as a million years they don't get more than a hundred or two hundred light years from their birthplaces before exploding as supernovae. That is why they are restricted to the spiral arms of the Milky way in massive star clusters and loosely bound groups called associations. The Sun on the other hand has circled the galaxy some 20 times since its birth and spends most of it's time between the spiral arms, where mostly middle aged and old stars reside. It has lazily orbited the center of the galaxy with a period of some 250 million years and thus left it's birthplace far behind before the Earth even had started to develop it's first oceans. Massive stars cannot become white dwarfs because they can't shed enough mass quickly enough to get below the natural mass limit for white dwarfs. A white dwarf is a dead core of a star usually made of carbon and oxygen, but silicon, helium, hydrogen and other elements are in their makeup as well. If it's mass exceeds 1.4 times that of the Sun, a runaway thermonuclear reaction will start in the center and quickly consume the whole star, blowing it apart like a titanic thermonuclear bomb. Red dwarfs have masses from about .5 Suns down to .08 Suns. They burn their hydrogen fuel so slowly, they last for a trillion years or longer. They will be around after all the more massive stars have long since faded away into invisibility. These stars are most definitely co-mingled with very hot, massive and luminous blue giants, but they're so faint we can't see them unless they are in our local neighborhood whereas a massive star can be visible from another galaxy.