Cepheid variable
Videos
A Cepheid variable is a type of variable star that pulsates radially, varying in both diameter and temperature. It changes in brightness, with a well-defined stable period and amplitude. Cepheids are
RS Puppis, one of the brightest known Cepheid variable stars in the Milky Way galaxy (Hubble Space Telescope)
Illustration of Cepheid variables (red dots) at the center of the Milky Way
Light curve of Delta Cephei, the prototype of classical cepheids, showing the regular variations produced by intrinsic stellar pulsations
Polaris
Videos
Polaris is a yellow supergiant star in the northern circumpolar constellation of Ursa Minor. It is designated α Ursae Minoris and is commonly called the North Star. With an apparent magnitude that flu
Cepheid variable
…known luminosity to its observed brightness, calibrated by direct observation of the parallax distance to the closest Cepheids such as RS Puppis and Polaris. Cepheids change brightness due to the κ–mechanism, which occurs when the opacity of a star's atmosphere increases with temperature rather than decreasing…
Polaris components as seen by the Hubble Space Telescope
A typical star trail photograph taken in the Northern Hemisphere, with Polaris in the center
Polaris azimuths vis clock face analogy.
Artist's conception showing supergiant Polaris Aa, dwarf Polaris Ab, and the distant dwarf companion Polaris B