Nature of the Long-period Variable Stars

Abstract

R. M. SCOTT has an article on the long-pariod variable stars in the Telescope of September-October, which provides a popular description of the type of star of which Mira is a prototype. The spectra of these stars reveal that they are cold enough to contain molecules, and yet sufficiently hot to show the bright lines of hydrogen and ionized metals, and a brief explanation of the probable reason for this follows. Assuming that these stars are pulsating, we can picture a small core about the size of our sun surrounded by an atmosphere extending to a distance comparable with that of the earth from the sun. Viewed from a distance, one of these stars would present the appearance of a luminous fuzzy ball, deep in a hazy murk, and it is easy to imagine flames similar to solar prominences hovering deep in the smoky atmosphere near the luminous core. Then as the star approaches minimum the atmosphere would become darker and more clouded and the core a deeper red, the eruptions practically disappearing. It is possible that these red variables may be a link in the evolutionary chain, great numbers of stars starting their lives as red variables and then outgrowing their adolescent pulsations. On the other hand, red-variable pulsations may represent the palsy of stellar old age, though the former theory is the more popular of the two. At present this type of star presents a problem which can only be solved by much more investigation.