---
title: "History of astronomy"
chunk: 11/11
source: "https://en.wikipedia.org/wiki/History_of_astronomy"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:59:16.412764+00:00"
instance: "kb-cron"
---

With the accumulation of large sets of astronomical data, teams like the Harvard Computers rose in prominence which led to many female astronomers, previously relegated as assistants to male astronomers, gaining recognition in the field. The United States Naval Observatory (USNO) and other astronomy research institutions hired human "computers",  who performed the tedious calculations while scientists performed research requiring more background knowledge. A number of discoveries in this period were originally noted by the women "computers" and reported to their supervisors. Henrietta Swan Leavitt discovered the cepheid variable star period-luminosity relation which she further developed into a method of measuring distance outside of the Solar System.
A veteran of the Harvard Computers, Annie J. Cannon developed the modern version of the stellar classification scheme in during the early 1900s (O B A F G K M, based on color and temperature), manually classifying more stars in a lifetime than anyone else (around 350,000).
The twentieth century saw increasingly rapid advances in the scientific study of stars.
Karl Schwarzschild discovered that the color of a star and, hence, its temperature, could be determined by comparing the visual magnitude against the photographic magnitude. The development of the photoelectric photometer allowed precise measurements of magnitude at multiple wavelength intervals. In 1921 Albert A. Michelson made the first measurements of a stellar diameter using an interferometer on the Hooker telescope at Mount Wilson Observatory.

Important theoretical work on the physical structure of stars occurred during the first decades of the twentieth century. In 1913, the Hertzsprung–Russell diagram was developed, propelling the astrophysical study of stars.
In Potsdam in 1906, the Danish astronomer Ejnar Hertzsprung published the first plots of color versus luminosity for these stars. These plots showed a prominent and continuous sequence of stars, which he named the Main Sequence.
At Princeton University, Henry Norris Russell plotted the spectral types of these stars against their absolute magnitude, and found that dwarf stars followed a distinct relationship. This allowed the real brightness of a dwarf star to be predicted with reasonable accuracy.
Successful models were developed to explain the interiors of stars and stellar evolution. Cecilia Payne-Gaposchkin first proposed that stars were made primarily of hydrogen and helium in her 1925 doctoral thesis. The spectra of stars were further understood through advances in quantum physics. This allowed the chemical composition of the stellar atmosphere to be determined.
As evolutionary models of stars were developed during the 1930s, Bengt Strömgren introduced the term Hertzsprung–Russell diagram to denote a luminosity-spectral class diagram.
A refined scheme for stellar classification was published in 1943 by William Wilson Morgan and Philip Childs Keenan.

The existence of the Milky Way, Earth's home galaxy, as a separate group of stars was only proven in the 20th century, as was the knowledge that other galaxies exist and that most of them are moving away from each other. The "Great Debate" between Harlow Shapley and Heber Curtis, in the 1920s, concerned the nature of the Milky Way, spiral nebulae, and the dimensions of the universe.
With the advent of quantum physics, spectroscopy was further refined.
The Sun was found to be part of a galaxy made up of more than 1010 stars (10 billion stars). The existence of other galaxies, one of the matters of the great debate, was settled by Edwin Hubble, who identified the Andromeda Nebula as a different galaxy, and many others at large distances and receding, moving away from our galaxy.
Physical cosmology, a discipline that has a large intersection with astronomy, made huge advances during the 20th century, with the model of the hot Big Bang heavily supported by the evidence provided by astronomy and physics, such as the redshifts of very distant galaxies and radio sources, the cosmic microwave background radiation, Hubble's law and cosmological abundances of elements.

== See also ==

== References ==

== Further reading ==
Aaboe, Asger (2001). Episodes from the Early History of Astronomy. Springer-Verlag. ISBN 0-387-95136-9.
Berry, Arthur (1898). A Brief History of Astronomy – via Internet Archive.
Dreyer, J. L. E. (1953) [1906]. History of Astronomy from Thales to Kepler (2nd ed.). Dover Publications.
Eastwood, Bruce (2002). The Revival of Planetary Astronomy in Carolingian and Post-Carolingian Europe. Variorum Collected Studies Series. Vol. CS 279. Ashgate. ISBN 0-86078-868-7.
Hodson, F. R., ed. (1974). The Place of Astronomy in the Ancient World: A Joint Symposium of the Royal Society and the British Academy. Oxford University Press. ISBN 0-19-725944-8.
Hoskin, Michael (2003). The History of Astronomy: A Very Short Introduction. Oxford University Press. ISBN 0-19-280306-9.
Hoskin, Michael (2011). Discoverers of the Universe: William and Caroline Herschel. Princeton University Press. ISBN 978-0691148335.
Magli, Giulio (2004). "On the possible discovery of precessional effects in ancient astronomy". arXiv:physics/0407108.
Neugebauer, Otto (1969) [1957]. The Exact Sciences in Antiquity (2 ed.). Dover Publications. ISBN 978-0-486-22332-2.
Pannekoek, Anton (1989). A History of Astronomy. Dover Publications.
Walker, Christopher, ed. (1996). Astronomy before the telescope. British Museum Press. ISBN 0-7141-1746-3.

== External links ==
 Media related to History of astronomy at Wikimedia Commons
Astronomy & Empire, BBC Radio 4 discussion with Simon Schaffer, Kristen Lippincott & Allan Chapman (In Our Time, May 4, 2006)
Bibliothèque numérique de l'Observatoire de Paris (Digital library of the Paris Observatory)
Caelum Antiquum: Ancient Astronomy and Astrology Resources on LacusCurtius
Mesoamerican Archaeoastronomy:  A Review of Contemporary Understandings of Prehispanic Astronomical Knowledge
UNESCO-IAU Portal to the Heritage of Astronomy