Henrietta Swan Levitt

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Henrietta Swan Leavitt
Upper body and face of Henrietta Swan Leavitt
BornJuly 4, 1868
DiedDecember 12, 1921(1921-12-12) (aged 53)
Alma materRadcliffe College, Oberlin College
Known forLeavitt's law: the period-luminosity relationship for Cepheid variables
Scientific career
FieldsAstronomy
InstitutionsHarvard University
Plot from a paper prepared by Leavitt in 1912. The horizontal axis is the logarithm of the period of the corresponding Cepheid, and the vertical axis is its magnitude. The lines drawn connect points corresponding to the stars' minimum and maximum brightness, respectively.[1][2]


Henrietta Swan Leavitt (/ˈlɛvɪt/; July 4, 1868 – December 12, 1921) was an American astronomer.

After she graduated from Radcliffe College, she worked at the Harvard College Observatory.

She examined photographic plates to measure and catalog the brightness of stars. She discovered the relation between the luminosity and the period of Cepheid variables.[3]

This gave astronomers with the first "standard candle" to measure the distance to faraway galaxies.[4][1]

She discovered the period-luminosity relationship for Cepheid variables. Her work allowed astronomers to measure distances up to about 20 million light years. As a result of this, it is now known that our own galaxy, the Milky Way, has a diameter of about 100,000 light years.

After Leavitt's death, Edwin Hubble established that the universe is expanding (see Hubble's law). He used Leavitt's period-luminosity relation, and the galactic spectral shifts first measured by Vesto Slipher at Lowell Observatory.

References[change | change source]

  1. 1.0 1.1 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.
  2. Malatesta, Kerri (April 13, 2010). "Delta Cephei". American Association of Variable Star Observers. Retrieved January 1, 2020.
  3. Johnson, George 2005. Miss Leavitt's stars: the untold story of the woman who discovered how to measure the universe. New York: W.W. Norton & Company. ISBN 978-0-393-05128-5
  4. Leavitt, Henrietta S. (1908). "1777 variables in the Magellanic Clouds". Annals of Harvard College Observatory. 60: 87–108. Bibcode:1908AnHar..60...87L.