Henrietta Swan Leavitt

Henrietta Swan Leavitt
Upper body and face of Henrietta Swan Leavitt
Leavitt, c. 1898
Born(1868-07-04)July 4, 1868
Lancaster, Massachusetts, U.S.
DiedDecember 12, 1921(1921-12-12) (aged 53)
Cambridge, Massachusetts, U.S.
Education
Known forLeavitt's Law:[1] the period-luminosity relationship for Cepheid variables
Scientific career
FieldsAstronomy
InstitutionsHarvard University, Oberlin College

Henrietta Swan Leavitt (/ˈlɛvɪt/; July 4, 1868 – December 12, 1921[2]) was an American astronomer.[1] Her discovery of how to effectively measure vast distances to remote galaxies led to a shift in the scale and understanding of the scale and the nature of the universe.[3] Nomination of Leavitt for the Nobel Prize had to be halted because of her death.[4][5]

A graduate of Radcliffe College, she worked at the Harvard College Observatory as a human computer, tasked with measuring photographic plates to catalog the positions and brightness of stars. This work led her to discover the relation between the luminosity and the period of Cepheid variables. Leavitt's discovery provided astronomers with the first standard candle with which to measure the distance to other galaxies.[6][7]

Before Leavitt discovered the period-luminosity relationship for Cepheid variables (sometimes referred to as Leavitt's Law), the only techniques available to astronomers for measuring the distance to a star were based on stellar parallax. Such techniques can only be used for measuring distances out to several hundred light years. Leavitt's great insight was that while no one knew the distance to the Small Magellanic Cloud, all its stars must be roughly the same distance from Earth. Therefore, a relationship she discovered in it, between the period of certain variable stars (Cepheids) and their apparent brightness, reflected a relationship in their absolute brightness. Once calibrated by measuring the distance to a nearby star of the same type via parallax, her discovery became a measuring stick with vastly greater reach.[8]

After Leavitt's death, Edwin Hubble found Cepheids in several nebulae, including the Andromeda Nebula, and, using Leavitt's Law, calculated that their distance was far too great to be part of the Milky Way and were separate galaxies in their own right. This settled astronomy's Great Debate over the size of the universe. Hubble later used Leavitt's Law, together with galactic redshifts, to establish that the universe is expanding (see Hubble's law).

  1. ^ a b Johnson, Kirk (March 27, 2024). "Overlooked No More: Henrietta Leavitt, Who Unraveled Mysteries of the Stars - The portrait that emerged from her discovery, called Leavitt's Law, showed that the universe was hundreds of times bigger than astronomers had imagined". The New York Times. Archived from the original on March 27, 2024. Retrieved March 28, 2024.
  2. ^ "Henrietta Swan Leavitt – Biography". Maths History. August 2017. Retrieved December 10, 2022.
  3. ^ Cite error: The named reference carnegiescience was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Singh was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Johnson was invoked but never defined (see the help page).
  6. ^ Leavitt, Henrietta S. (1908). "1777 variables in the Magellanic Clouds". Annals of Harvard College Observatory. 60: 87–108. Bibcode:1908AnHar..60...87L.
  7. ^ Leavitt, Henrietta S.; Pickering, Edward C. (March 1912). "Periods of 25 Variable Stars in the Small Magellanic Cloud". Harvard College Observatory Circular. 173: 1–3. Bibcode:1912HarCi.173....1L.
  8. ^ Cite error: The named reference PLhistory was invoked but never defined (see the help page).