These are the so-called R-type stars of the Northern Crown. In these variable stars, from time to time, the brightness slowly weakens by 1-9 magnitudes, after which it gradually returns to its original value. It is assumed that the brilliance of these stars, which have an excess of carbon compared to the Sun, is diminished by carbon particles formed in the cloud ejected by the star.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.