HENRIETTA SWAN LEAVITT

Henrietta Swan Leavitt, American astronomer, is known for his work on variable stars.
She is the daughter of George Roswell Leavitt, Congregational minister, and Henrietta Swan Leavitt Kendrick. She studied astronomy at Radcliffe College. After graduating in 1892, it remains one more year as a graduate student.
After this period of intensive study, she travels and gets a job as an assistant at Harvard College Observatory. In 1902, after obtaining a permanent position, she was promoted to Chief of photometry.
During the years 1880-1890, Edward Pickering, director of the observatory, began a comprehensive program aimed at determining the visual magnitudes. Leavitt participated in the program.
In 1907, Pickering launched a project to establish a standard photographic sequence with stars near the north celestial pole. Leavitt is involved in analyzing the stars of magnitude 4 to 21, photographed nearly 300 plates from 13 different telescopes.
She studies the plates obtained at the Observatory of Arequipa in Peru. Of this observatory, owned by Harvard, one could observe the Magellanic Clouds, galaxies associated with ours.
In 1908, following a study of 16 Cepheid variable stars of the type, Leavitt discovered 1777 variables in the Magellanic Clouds, determines their period.
In 1912, it extends its analysis to 25 stars. It establishes a graphical representation of data and find that the apparent magnitude decreases linearly with the logarithm of the period.

Leaviit realizes that his discovery can be a valuable indicator of the intrinsic luminosity and hence, provide a precise determination of distances.
Pickering's discouraging to pursue this promising avenue, he hopes it works for him simply by collecting the data, without interpretation.
It Hertzsprung that recognizes the following year, the same type as those of Leavitt Cepheids in the Magellanic Clouds.
Leavitt using the relationship, it can determine the distance of the Clouds. Henrietta Leavitt acquires a reputation fully justified.
She continues her work and discovered 2,400 variable stars, half of those known at the time.
The relationship found by Henrietta Leavitt gives a powerful way to determine the distances of galaxies with Cepheids. Using the relation of Henrietta Leavitt, Hubble showed in 1923 that the Andromeda galaxy was located more than a million light years.
Given its apparent size, it had to be of a size comparable to that of the Milky Way.
Henrietta died of cancer, December 12, 1921 at the age of 53.

Image: Henrietta Swan Leavitt discovered and cataloged variable stars located in the Magellanic Clouds.
In 1912, from its catalog, she discovered that the brightness of Cepheid variables is proportional to their period of variation of brightness.