Star Reveals A Secret 

To measure distances in the Universe, astronomers use Cepheids, a family of variable stars whose luminosity varies with time. Their role as distance calibrators has brought them attention from researchers for more than a century.

While it was thought that nearly everything was known about the prototype of Cepheids, named Delta Cephei, a team of researchers at the University of Geneva (UNIGE), the Johns Hopkins University, and the European Space Agency (ESA), have now discovered that this star is not alone, but that it has a hidden companion. A revelation published in The Astrophysical Journal.

Delta Cephei, prototype of Cepheids, which has given its name to all similar variable stars, was discovered 230 years ago by the English astronomer, John Goodricke. Since the early 20th century, scientists have been interested in measuring cosmic distances using a relationship between these stars’ periods of pulsation and their luminosities (intrinsic brightness), discovered by the American Henrietta Leavitt.

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