Their pulsations are related to the same helium instability strip on the Hertzsprung-Russell diagram as that of classical Cepheids.

As a member of the category of variable stars known as classical Cepheids, it has a regular pulsation frequency that is determined by its mass.

The North Star (Polaris) is the closest classical Cepheid, but it has many peculiarities and its distance is not certain.

This is the first classical Cepheid to have a dynamical mass determined from its orbit.

However, the namesake for classical Cepheids is the star Delta Cephei, discovered to be variable by John Goodricke a few months later.

The following relation can be used to calculate the distance to Galactic and extragalactic classical Cepheids:

Over 700 classical Cepheids are known in the Milky Way Galaxy, and several thousand extragalactic Cepheids have been discovered.

The Hubble Space Telescope has identified classical Cepheids in NGC 4603, which is 100 million light years distant.

The following relations can also be used to calculate the distance to classical Cepheids:

The North Star (Polaris) is the closest classical Cepheid, although the star exhibits many peculiarities and its distance is a topic of active debate.