William Atkins
Tuesday, 30 September 2008 00:07
Science -
Space
Page 2 of 3
A Cepheid variable (or, simply Cepheid) is a specific type of variable star that has a period of variability closely tied with its absolute luminosity. They are generally giant, bright yellow stars.
Because of their variability-luminosity correlation, Cepheid variable stars are used to determine distances within our galaxy.
And, because they are so bright (luminous), they can be seen by astronomers on Earth over 60 million light-years away.
Cepheid variable stars were first discovered in 1595. The variability of two Cepheids—Eta Aquilae and Delta Cephei—were first discovered in 1783 and 1784, respectively.
Eta Aquilae is a star in the constellation Aquila that is about 1,200 light-years from the Sun. Delta Cephei is a binary star system that is about 891 light-years away from the Sun in the constellation of Cepheus. Cepheids were named after Delta Cephei.
The relationship between their period and luminosity was discovered in 1908 and confirmed in 1912 by American astronomer Henrietta Swan Leavitt. The discovery paved the way for using Cepheid variables as measurement markers for the galaxy.
Because of their variability/luminosity correlation, Cepheid variable stars are used to determine distances within our galaxy. About 500 Cepheids have been discovered in our Milky Way Galaxy.
Please read on as the astronomers relate some of their ideas concerning their Cepheid variable star "calling" plan.
