An Etymological Dictionary of Astronomy and Astrophysics
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A Cepheid variable in which two or more almost identical periods of variability pass into and out of phase with each other, producing periodic amplitude fluctuations in their light curves. Beat periods are typically about 2 hours.

→ beat; → Cepheid.

A subtype of classical → Cepheid variable stars that show a bump on the descending branch of their → light curve.

Bump "a relatively abrupt convexity or bulge on a surface," probably imitative of the sound of a blow; → Cepheid.

Quzdâr, from quz "hump," variant of kuž, → convex, + -dâr "possessing," from dâštan "to have, possess." Zokdâr, from Lori zok "a raised spot, a bulge," cf. Northern Fârs Âbâdé dialect lok " swellimg, knob;" Kefeusi, → Cepheid.

A class of luminous, → yellow supergiants that are pulsating variables and whose period of variation is a function of their → luminosity. These stars expand and contract at extremely regular periods, in the range 1-50 days. Their highest brightness and surface temperature occur when their expansion velocity is greatest. Similarly, their minima in brightness and temperature occur when they are in the contraction phase. The longer the period, the more luminous the star. The process that drives the pulsation of → Cepheid variables is the → kappa mechanism. In fact, Cepheids provide one of the most powerful tools for measuring distances to other galaxies (→ period-luminosity relation). However, this method is limited to the distance of the → Virgo cluster of galaxies (15-20 → Mpc) even with the → HST or the largest ground-based telescopes. One particularly special Cepheid is the North Star, → Polaris. See also → RR Lyrae star.

Named after the prototype → Delta Cephei discovered by John Goodricke in 1784. → Cepheus.

A → variable star belonging to the class of → Cepheids.

→ Cepheid; → variable.

An old name for a class of pulsating variable stars with small variations in amplitude, also called an AI Velae star or delta Scuti star. They lie in the lower part of the Cepheid instability strip.

→ dwarf; → Cepheid.

A → Cepheid star of → spectral type A-F with regular pulsation period of 1-3 hours and with small variations in amplitude. This group is also known as δ Scuti stars.

→ ultra-; → short; → period; → Cepheid.