AS102 Study Guide - Final Guide: Delta Cephei, Henrietta Swan Leavitt, John Goodricke
Document Summary
We now know that the funny-shaped edges in the outer reaches of the galaxy were caused by clouds of dust and gas that prevents visible starlight from reaching earth and the herschels telescope in the late 1700s. This view of the universe remained the accepted view until the early part of the twentieth century when things started to unravel. It was well known by this time that some stars pulsate; their intensity varies regularly with periods ranging from days to months. Such stars are called cepheids because one of the first of such stars was discovered in the constellation cepheus (the star delta cephei was discovered by john goodricke in 1784). 1912, henrietta leavitt realized that there appeared to be a fairly linear relationship between the period of brightness variation for a cepheid and its average brightness. In the graph shown below the curve labelled type i cepheids is the one discovered by.
