For standard candles, the team used Cepheid variable
stars, which pulsate at a rate that is correlated with their brightness, and type la supernovas, whose brightness properties are well-understood.
Oscillations occur not only in mechanical systems but also in dynamic systems in virtually every area of science: for example the beating human heart, business cycles in economics, predator-prey population cycles in ecology, geothermal geysers in geology, vibrating strings in musical instruments, periodic firing of nerve cells in the brain, and the periodic swelling of Cepheid variable
stars in astronomy.
Harlow Shapley became an astronomer at Mount Wilson Observatory; studied Cepheid variable
And be sure to check in on the classic Cepheid variable
we mentioned last month, Delta ([delta]) Cephei, now high in the northwest.
A Cepheid Variable
is usually a population I giant yellow star, pulsing regularly by expanding and contracting, resulting in a regular oscillation of its luminosity.
This is important because Polaris A is a Cepheid variable
Quantifying the shapes of Cepheid variable
star light curves is a technique that has been in use for the past several decades.
Since the launch of NASA's Hubble Space Telescope in 1990, the team has observed 18 galaxies up to 65 million light years away and discovered almost 800 Cepheid variable
stars, a special class of pulsating star used for accurate distance measurement.
By 1912 Leavitt had worked out a method for determining the luminosity of a Cepheid variable
from its period.
The three variable stars are, west to east: Delta ([delta]) Cephei, the prototype of the Cepheid variable
class; Omicron (o) Ceti (Mira), the prototype of long-period or Mira variables; and Beta ([beta]) Persei (Algol), the prototype of eclipsing binaries.
We present analysis of two double model Cepheid variable
stars, BQ Serpens and VX Puppis.
It is one of the most luminous in the class of so-called Cepheid variable