Overview
T Cephei is a luminous, red giant star located in the constellation Cepheus. It is observed as a long-period variable: its visible brightness changes over time because the star undergoes radial pulsations. As a cool, late-type giant it appears distinctly red to telescopes and contributes to studies of evolved stars.
Characteristics
As a late-type (M-class) giant, T Cephei has a cool photosphere and strong molecular absorption bands in its spectrum. Its radius is far larger than the Sun's—typically tens to a few hundred times the solar radius for stars of this class—and it sheds material into a surrounding envelope as it evolves.
Variability and pulsation
T Cephei belongs to the family of long-period variable stars that show substantial light changes driven by pulsation of the outer layers. These pulsations change the star's temperature, radius and brightness on timescales of months to a few years. Observations of such cycles yield information about stellar structure and the mechanics of pulsation.
Evolutionary context
Stars like T Cephei are in advanced stages of stellar evolution, typically on the asymptotic giant branch (AGB) or a closely related phase. During this stage they experience enhanced mass loss, form dust in their winds, and enrich the interstellar medium with heavy elements. Eventually such stars will lose their outer layers and leave behind a white dwarf.
Scientific importance and observation
T Cephei and similar variables are useful probes of late stellar evolution, mass-loss processes and period–luminosity relations used in distance studies. Amateur and professional astronomers monitor their light curves to track changes in period and amplitude. For general resources and observational data, see further reading.