Why are upper-main-sequence stars unlikely sites for intelligent civilizations?
The “upper main sequence” is the name for massive stars, which have high luminosity and relatively short lifetimes (often less than a billion years). While we can only speculate about where and when intelligence and civilizations arise, it seems reasonable to expect this to happen for older planetary systems rather than young ones. We know it took 4.5 billion years for a technical civilization to arise on Earth.
