Previous observations looked at brighter, aging red giant stars, which are not as plentiful because they represent a brief episode in a star's lifetime. (sciencedaily.com)
Low - mass stars also become red giants towards the end of their lives, expanding and cooling at the surface. (scienceinschool.org)
They are cool, red giants with large mass loss in the form of strong stellar winds, and are typically long - period variables. (alma-telescope.jp)