Category Archives for "Science"

December 28, 2016

How the Ladies of Harvard University took the Measure of the Stars

Henrietta Leavitt’s discoveries allowed astronomers to measure distances between stars and galaxies.

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What’s it about?

In the late 19th century Harvard University was the first to take advantage of the growing numbers of educated women, employing a group at the Harvard College Observatory. Known as “computers”, they charted the position and brightness of stars on a daily basis by applying mathematical formulae to the observations of their male colleagues who watched the sky.

How the Ladies of Harvard University took the Measure of the Stars:

  1. The introduction of photography at the Harvard Observatory allowed the capturing of the skies on eight by ten-inch glass plates. It was the woman at Harvard that were assigned these photographic duties.
  2. Williamina Fleming discovered 10 nova’s, doubling the number observed at the time she started.
  3. Anne Cannon recorded hundreds of thousands of stars and invented a classification system for stars that astronomers still use today.
  4. Henrietta Leavitt became the first person to realize that the cyclical dimming and brightening of variable stars  related to their brightness. This allowed astronomers to measure how far apart they were and to establish the distances between stars and galaxies.
  5. Cecilia Payne discovered the abundance of hydrogen in stars.  She was the first Harvard Student (man or woman) to be awarded a PhD in astronomy,
  6. A stars spectrum could be recorded for the first time.


These spectra resemble long rainbow-coloured strips (rendered in black and white on the plates’ photographic emulsion) interspersed with numerous dark lines. Scientists would come to understand that the gaps in a spectrum are due to the absorption of light by the atoms of chemical elements that compose a star’s outer layers.

The ability to divine a star’s constituents from its spectrum “made the chemist’s arms millions of miles long”.

Stellar spectroscopy would also reveal other physical attributes of stars such as their temperature, eventually giving rise to the new field of astrophysics.

 Take Away Points and Context

  • The woman at Havard made remarkable discoveries at a time when woman had few rights.
  • They were often given humdrum labors to undertake, but made the best of what they did.
  • Had they been less occupied with these labours they may have achieved even more than they did.


Full article:

Looking at the stars: How women rose to the top of American astronomy

The Economist

The Glass Universe: How the Ladies of the Harvard Observatory Took the Measure of the Stars.

By Dava Sobel.
Viking; 324 pages; $30.
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