Female Scientist Discovers the Distance Key


Photo Courtesy of wikipedia

“Next time you “Wish Upon a Star” you may wish to thank Henrietta Swan Leavitt, who discovered the key for finding the distance to stars much further away  or When Buzz Lightyear exclaimed, “To infinity and beyond!”

The parallax method, measuring the distance between our solar system and a star up to 1600 light years away, used to measure the distances to nearby stars, pioneered by Bessel and others could only be used on stars closer than 100 light years away.  But most stars and other galaxies are far beyond that, stated distancecarnegiescience.edu.

The key for finding the distance to stars much further away was discovered by Henrietta Swan Leavitt who worked at Harvard College Observatory as a “computer,” one of several women paid 25 to 30 cents per hour to extract data from thousands of photographic plates, reported cosmology.com.

Leavitt became curious about whether there might be a relationship between the brightness of a variable star and the length of its period (how long it takes for the star to get brighter, dimmer, then brighter again). That was difficult because she did not know the intrinsic brightness of any given variable. She solved the problem by restricting her search to a particular kind of variable star known as Cepheid variables that reside in the Small Magellanic Cloud—a distant star cluster. She reasoned that all stars in the cluster must be approximately the same distance from Earth, stated cosmology.com.

Leavitt discovered 2,400 new variable stars, about half of those known at the time, as well as four novae. But her discovery of the relation between the luminosity, or brightness, of a certain group of pulsating stars known as Cepheids and their variability, or periods of change in pulsation, made it possible to accurately determine stellar distances, in particular vastly greater distances than had ever before been possible reported howstuffworks.com.

Leavitt’s discovery ignited a scientific powder trail whose blaze brought fame and glory to many of her peers: without it, Edwin Hubble might never have been able to show that the spiral nebula Andromeda was not located at the edge of our galaxy, as had been previously thought, but almost a million light years away, stated aviso.com.

Nor might the Danish astronomer Ejnar Hertzsprung been able to measure the parallax of many of the nearby Cepheid variables; even though while using Leavitt’s discovery to his advantage, a slip of his pen is alleged to have caused him to underestimate the stars’ distance by a factor of 10.

By discovering the distance key, Henrietta Swan Leavitt made possible all of the subsequent discoveries in astronomy of the 19th and 20th centuries, reported cosmology.com.