# Henrietta Swan Leavitt

> American astronomer and human calculator (1868–1921)

**Wikidata**: [Q110181](https://www.wikidata.org/wiki/Q110181)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Henrietta_Swan_Leavitt)  
**Source**: https://4ort.xyz/entity/henrietta-swan-leavitt

## Summary
Henrietta Swan Leavitt was an American astronomer and human calculator (1868–1921) who discovered a relationship between the luminosity and period of Cepheid variable stars, a critical breakthrough that enabled the measurement of cosmic distances. Her work laid the foundation for modern cosmology and the understanding of the universe's vast scale.

## Biography
- Born: July 4, 1868, Lancaster, Massachusetts, United States
- Nationality: United States
- Education: Oberlin College, Radcliffe College, Harvard University
- Known for: Developing the period-luminosity relationship for Cepheid variable stars
- Employer(s): Harvard College Observatory, American Association of Variable Star Observers
- Field(s): Astronomy

## Contributions
- **Cepheid Variable Stars**: Discovered the period-luminosity relationship for Cepheid variable stars, which became a "standard candle" for measuring astronomical distances. This work was published in 1912 and revolutionized cosmology by providing a method to calculate the size of the universe.
- **Photographic Plate Analysis**: As a "human computer" at Harvard, Leavitt meticulously analyzed thousands of photographic plates to catalog variable stars, contributing to the Harvard Computers' groundbreaking work in astrophysics.
- **Variable Star Research**: Her research on variable stars, particularly RR Lyrae stars, expanded understanding of stellar evolution and the structure of the Milky Way galaxy.

## FAQs
**What was Henrietta Swan Leavitt's most significant contribution to astronomy?**
Henrietta Swan Leavitt's discovery of the period-luminosity relationship for Cepheid variable stars was pivotal. This relationship allowed astronomers to measure cosmic distances accurately, a breakthrough that underpinned modern cosmology and our understanding of the universe's vast scale.

**Where did Henrietta Swan Leavitt work during her career?**
Leavitt worked at the Harvard College Observatory, where she was part of the Harvard Computers team. She later became a member of the American Association of Variable Star Observers, contributing to variable star research throughout her career.

**What is a "standard candle" in astronomy?**
A "standard candle" is a type of star with known luminosity, which allows astronomers to calculate distances to celestial objects by comparing their apparent brightness. Henrietta Swan Leavitt's work on Cepheid variables established them as a primary standard candle for measuring cosmic distances.

**How did Henrietta Swan Leavitt's work influence modern cosmology?**
Her discovery provided a method to measure the size of the universe, enabling Edwin Hubble to later prove the universe's expansion. This work remains foundational in cosmology, shaping our understanding of the cosmos.

## Why They Matter
Henrietta Swan Leavitt's work on Cepheid variable stars transformed astronomy by providing a reliable method to measure cosmic distances. Her discovery, the period-luminosity relationship, became the cornerstone for modern cosmology, enabling scientists like Edwin Hubble to prove the universe's expansion. Without her contributions, our understanding of the universe's vast scale and structure would be fundamentally incomplete. Her meticulous analysis of photographic plates and her role in the Harvard Computers' work also advanced astrophysics, setting a precedent for women in scientific research. Leavitt's legacy endures as a key figure in the history of astronomy, whose work continues to influence research today.

## Notable For
- **Standard Candle Discovery**: Established Cepheid variable stars as a primary "standard candle" for measuring cosmic distances.
- **Harvard Computers**: Contributed to the groundbreaking work of the Harvard Computers, a team of women astronomers who processed astronomical data.
- **Variable Star Research**: Expanded understanding of stellar evolution and the Milky Way galaxy through her studies of variable stars.
- **Foundational Cosmology**: Her work directly enabled the measurement of the universe's size and the discovery of its expansion.
- **Women in Astronomy**: Pioneered scientific research as a woman in a male-dominated field, inspiring future generations of astronomers.

## Body
### Early Life and Education
Henrietta Swan Leavitt was born on July 4, 1868, in Lancaster, Massachusetts. She attended Oberlin College, where she studied mathematics and astronomy. After graduating, she pursued advanced studies at Radcliffe College and Harvard University, where she became part of the prestigious Harvard Computers team.

### Career at Harvard College Observatory
Leavitt joined the Harvard College Observatory in 1902, where she worked as a "human computer," analyzing thousands of photographic plates to catalog variable stars. Her meticulous work contributed to the Harvard Computers' groundbreaking research in astrophysics.

### Discovery of the Period-Luminosity Relationship
In 1912, Leavitt published her discovery of the period-luminosity relationship for Cepheid variable stars. This relationship established Cepheids as a "standard candle," allowing astronomers to measure cosmic distances accurately. Her work revolutionized cosmology and laid the foundation for modern understanding of the universe's vast scale.

### Variable Star Research
Leavitt's research on variable stars, particularly RR Lyrae stars, expanded understanding of stellar evolution and the structure of the Milky Way galaxy. Her contributions to variable star research were recognized by the American Association of Variable Star Observers, of which she became a member.

### Legacy and Influence
Henrietta Swan Leavitt's work remains foundational in astronomy, directly enabling the measurement of the universe's size and the discovery of its expansion. Her legacy endures as a key figure in the history of astronomy, whose contributions continue to influence research today. Her pioneering role as a woman in scientific research also inspired future generations of astronomers.

## References

1. The Biographical Dictionary of Women in Science
2. Genealogics
3. Find a Grave
4. International Standard Name Identifier
5. Virtual International Authority File
6. NNDB
7. MacTutor History of Mathematics archive
8. Deportivo de La Coruña
9. Brockhaus Enzyklopädie
10. SNAC
11. Freebase Data Dumps. 2013
12. Forgotten Women: The Scientists
13. Autoritats UB
14. Quora