A Very Short History of Astronomy

2,500 BC - Stonehenge, one of the most famous sites in the world today, once served as a burial ground. Archaeoastronomers claim that Stonehenge represents an ancient observatory, and that the site had astrological and spiritual significance as well.

650 BC - Babylonian Venus tablet of Ammisaduqa is the oldest significant astronomical text that we possess. This document, recorded on cuneiform tablets, lists the first and last visible risings of Venus over a period of 21 years.


Stonehenge (Andrew Dunn); ................. Solar eclipse (Luc Viatour); .......... Thales; .................. Hipparchus

585 BC - Thales of Miletus predicts a solar eclipse. A battle in progress between the Lydians and the Medes is spontaneously halted by this eclipse.

150 BC - Hipparchus, the greatest astronomer of antiquity, uses parallax to determine that the distance to the Moon. In 134 BC, he discovers the precession of the equinoxes. Hipparchus ranks stars in six magnitude classes according to their brightness: he assignes '1' to the brightest stars, and '6' to the stars which can be barely seen with the naked eye.

46 BC - Julius Caesar adopted a calendar based upon the 365 1/4 day year length originally proposed by Greek astronomer Callippus. 46 BC had 445 days due to the errors that had accumulated in the pre-Julian calendar.

628 - Brahmagupta, the head of the astronomical observatory at Ujjain, writes a text on astronomy, Brahmasphutasiddhanta (The Opening of the Universe).

990 - Abu-Mahmud al-Khujandi builds a huge observatory near Tehran, Iran, and observes a series of meridian transits of the Sun, which allowed him to calculate the tilt of the Earth's axis relative to the Sun.

1054 - Crab Supernova (SN 1054) is observed on Earth by Chinese, Japanese, Arab, and American Indian astronomers. It was bright enough to see in daylight for 23 days.


Crab Nebula (NASA); ........................... Nicolaus Copernicus; ............................... De Revolutionibus

1543 - Nicolaus Copernicus' epochal book, De revolutionibus orbium coelestium, is published just before he died. This is often regarded as the starting point of modern astronomy.

1577 - Danish astronomer Tycho Brahe uses parallax to prove that comets are distant objects and not atmospheric phenomena. Tycho is credited with the most accurate astronomical observations of his time.

1609 - Johannes Kepler states his first two laws of planetary motion: 1. The orbit of every planet is an ellipse with the sun at a focus; 2. A line joining a planet and the sun sweeps out equal areas during equal intervals of time.


Tycho Brahe; ................... Johannes Kepler (Aldaron); .................... Galileo facing Inquisition

1610 - Galileo Galilei uses a small telescope to make the greatest astronomical discoveries of all time: the discovery of the four largest satellites of Jupiter, lunar mountains and craters, the phases of Venus, the Milky Way as a multitude of densely packed stars, and the observation and analysis of sunspots.

1687 - The Philosophiae Naturalis Principia Mathematica, mathematical principles of natural philosophy, a three-volume work by Isaac Newton, is published on 5 July 1687. It contains the foundation of classical mechanics, as well as the law of universal gravitation and a derivation of Kepler's laws for the motion of the planets.

1705 - Edmund Halley predicts the periodicity of Halley's comet and computes its expected path of return. In 1718, he discovers stellar proper motions by comparing his astrometric measurements with those of the Greeks.


Newton's telescope (Andrew Dunn); ........... Comet Halley (NASA); ....................... Charles Messier

1771 - Charles Messier publishes his first list of nebulae. The purpose of the catalog was to help comet hunters to distinguish between permanent and transient objects in the sky.

1781 - William Herschel discovers Uranus. He constructed more than 400 telescopes, discovered two moons of Saturn and two moons of Uranus, created extensive catalogs of nebulae and double stars, and concluded that the Milky Way is in the shape of a disk.

1814 - Joseph von Fraunhofer invents the spectroscope, and discovered 574 dark absorption lines appearing in the Sun's spectrum.

1838 - Friedrich Bessel, Friedrich Georg Wilhelm Struve, and Thomas Henderson measure stellar parallaxes, providing the first accurate measurements of interstellar distances.


Planet Uranus (NASA); ......................................... Herschel's 40 foot telescope; ................ Kirchhoff's first spectroscope

1860 - Gustav Kirchoff and Robert Bunsen discover that each element has its own distinct set of spectral lines and use this fact to explain the solar dark lines.

1908 - Henrietta Swan Leavitt discovers the Cepheid period-luminosity relation, providing an important yardstick for measuring distances in the Universe.

1910 - Ejnar Hertzsprung and Henry Russell study the relation between magnitudes and spectral types of stars. The Hertzsprung-Russell diagram represented a huge leap forward in understanding stellar evolution.

1915 - Albert Einstein completes his theory of general relativity. 'Matter tells space how to curve, space tells matter how to move'.

1922 - Alexander Friedmann finds a solution to the general relativity field equations which suggests a general expansion of space.

1923 - Edwin Powell Hubble profoundly changes our understanding of the universe by demonstrating the existence of other galaxies besides the Milky Way. Hubble also devises a system for classifying galaxies, according to their appearance in photographic images.


Andromeda Galaxy (John Lanoue); ........... Hubble's law (Brews Ohare); ............ George Gamow

1929 - Edwin Hubble and Milton Humason formulate the empirical Hubble's law -- the linear redshift-distance relation, thus showing the expansion of the universe.

1929 - George Gamow, a Russian-born physicist and cosmologist, proposes hydrogen fusion as the energy source for stars. He discovered alpha decay via quantum tunneling and worked on star formation, stellar nucleosynthesis, big bang nucleosynthesis, etc.

1930 - Clyde Tombaugh discovers the dwarf planet Pluto.

1930 - Subrahmanyan Chandrasekhar discovers the white dwarf maximum mass limit. The limit describes the maximum mass of a white dwarf star, above which a star will ultimately collapse into a neutron star or black hole.

1931 - Karl Guthe Jansky, American physicist and radio engineer, discovers radio waves emanating from the Milky Way. He is considered one of the founding figures of radio astronomy.

1931 - Roman Catholic priest Georges Lemaître proposes his 'hypothesis of the primeval atom', what became known as the Big Bang theory.

1933 - Fritz Zwicky applies the virial theorem to the Coma galaxy cluster and obtains evidence for unseen matter, what is now called dark matter. Zwicky was an original thinker, with many important contributions in astronomy.


Subrahmanyan Chandrasekhar; ... Cosmic Microwave Background (NASA); ... The Horn Antenna in Holmdel Township

1965 - Arno Penzias and Robert Wilson discover the cosmic microwave background radiation, predicted in 1948 by Ralph Alpher, George Gamow and Robert Herman.

1967 - Jocelyn Bell and Anthony Hewish discover the first radio pulsars, the greatest astronomical discovery of the twentieth century.

1971 - Cygnus X-1, a galactic X-ray source in the constellation Cygnus, is identified as a binary black hole candidate system.

1980 - Alan Guth, a theoretical physicist and cosmologist, proposes the inflationary Big Bang universe as a possible solution to the horizon and flatness problems.

1998 - Published observations of Type Ia supernovae by the High-z Supernova Search Team, followed in 1999 by the Supernova Cosmology Project, suggest that the expansion of the universe is accelerating.



Further reading:

Archaeoastronomy and Stonehenge
Astronomiae Historia
C41/ICHA website
Society for the History of Astronomy
Wikipedia History of astronomy