History of Astronomy Timeline

In the 6th century Bishop Gregory of Tours noted that he had learned his astronomy from reading Martianus Capella, and went on to employ this rudimentary astronomy to describe a method by which monks could determine the time of prayer at night by watching the stars.

Image source: Gregory of Tours

By the sixth century, Indian astronomers believed that comets were celestial bodies that re-appeared periodically. This was the view expressed by the astronomers Varahamihira and Bhadrabahu. During this century, astronomy was influenced by the Greek and Byzantine astronomical traditions.

Image source: Varāhamihira

In the 7th century the English monk Bede of Jarrow published an influential text, On the Reckoning of Time, providing churchmen with the practical astronomical knowledge needed to compute the proper date of Easter using a procedure called the computus. It remained important to clergy education well after the rise of the Universities in the 12th century.

Image source: Bede

This led to the emergence of the first astronomical observatories in the Muslim world by the early 9th century. In the ninth century, Persian astrologer Albumasar was thought to be one of the greatest astrologers of that time, whose manuals profoundly influenced Muslim intellectual history and, through translations, that of western Europe and Byzantium.

Image source: Astronomy in the medieval Islamic world

In the late tenth century, a huge observatory was built near Tehran, Iran, by the astronomer Abu-Mahmud al-Khujandi who observed a series of meridian transits of the Sun, which allowed him to calculate the tilt of the Earth's axis relative to the Sun.

Image source: Abu-Mahmud Khujandi

Building on an astronomical background circulating since the 9th century, in the 10th century European scholars such as Gerbert of Aurillac began to travel to Spain and Sicily to seek out learning which they had heard existed in the Arabic-speaking world. By the 12th century, scholars translated advanced astronomical texts into Latin from Arabic and Greek.

Image source: Pope Sylvester II

In 1006, Ali ibn Ridwan observed SN 1006, the brightest supernova in recorded history, and left a detailed description of the temporary star.

Image source: SN 1006

The supernova that created the Crab Nebula in 1054 is an example of a 'guest star' observed by Chinese astronomers, although it was not recorded by their European contemporaries. Detailed records of astronomical observations had been kept in China from about the 6th century BC.

Image source: Crab Nebula

In 11th-century Persia, Omar Khayyám compiled many tables and performed a reformation of the calendar that was more accurate than the Julian and came close to the Gregorian.

Image source: Omar Khayyam

Natural philosophy (particularly Aristotelian physics) was separated from astronomy by Ibn al-Haytham (Alhazen) in the 11th century, by Ibn al-Shatir in the 14th century, and Qushji in the 15th century.

Image source: Ibn al-Haytham

In the 14th century, Nicole Oresme showed that neither scriptural texts nor physical arguments against the movement of the Earth were demonstrative, adducing the argument of simplicity for a moving Earth. However, he concluded that 'the heavens do move and not the earth.'

Image source: Nicole Oresme

In the 15th century, Cardinal Nicholas of Cusa suggested in some of his scientific writings that the Earth revolved around the Sun, and that each star is itself a distant sun.

Image source: Nicholas of Cusa

Polish astronomer Nicolaus Copernicus developed a heliocentric model depicting the planets orbiting the Sun. His De revolutionibus orbium coelestium was published in 1543, starting the Copernican Revolution.

Image source: De revolutionibus orbium coelestium

Tycho Brahe came on the astronomical scene with the publication of De nova stella, disproving conventional wisdom on the supernova SN 1572 and thereby the Aristotelian doctrine of the immutability of the heavens. He also created the Tychonic system, where the Sun, Moon and stars revolve around the Earth, but the other five planets revolve around the Sun.

Image source: Tycho Brahe

The first astronomer of the European Renaissance to suggest that the stars were distant suns was Giordano Bruno in his De l'infinito universo et mondi (1584). The idea became mainstream following Fontenelle's Conversations on the Plurality of Worlds (1686).

Image source: Giordano Bruno

The invention of the telescope in 1608 revolutionized the study of astronomy and played a key part in the Copernican Revolution.

Image source: History of the telescope

The first two of Kepler's laws of planetary motion were published in 1609. He completed the Rudolphine Tables in 1624, although they were not published for several years.

Image source: Johannes Kepler

Galileo discovered the four largest moons of Jupiter in 1610, now collectively known as the Galilean moons in his honor.

Image source: Galilean moons

While Galileo was able to avoid punishment for a little while, he was eventually tried and pled guilty to heresy in 1633. His book was banned, and he was put under house arrest until he died in 1642.

Image source: Galileo affair

At first, astronomical thought in America was based on Aristotelian philosophy, but interest in the new astronomy began to appear in Almanacs as early as 1659.

Image source: Great Debate (astronomy)

The Italian astronomer Geminiano Montanari recorded observing variations in luminosity of the star Algol in 1667, an early observation of a variable star.

Image source: Geminiano Montanari

Voltaire published a popular account in 1738, helping spread Newtonian ideas about astronomy and physics to a wider audience.

Image source: Voltaire

In 1748, the French Academy of Sciences offered a reward for solving the question of the perturbations of Jupiter and Saturn, which was eventually done by Euler and Lagrange. Laplace completed the theory of the planets, publishing from 1798 to 1825.

Image source: Perturbation (astronomy)

Edmond Halley succeeded John Flamsteed as Astronomer Royal in England and succeeded in predicting the return of the comet that bears his name in 1758.

Image source: Edmond Halley

William Herschel found the first new planet, Uranus, to be observed in modern times in 1781.

Image source: Uranus

The gap between the planets Mars and Jupiter disclosed by the Titius–Bode law was filled by the discovery of the asteroids Ceres and Pallas in 1801 and 1802, with many more following.

Image source: Ceres (dwarf planet)

The first solution to the problem of deriving an orbit of binary stars from telescope observations was made by Felix Savary in 1827. Observation of double stars gained increasing importance during the 19th century.

Image source: Binary star

The first direct measurement of the distance to a star (61 Cygni at 11.4 light-years) was made in 1838 by Friedrich Bessel using the parallax technique. In 1834, Bessel had also observed changes in the proper motion of Sirius and inferred a hidden companion.

Image source: Friedrich Bessel

In 1847, Maria Mitchell discovered a comet using a telescope, becoming a pioneering figure in American astronomy.

Image source: Maria Mitchell

In 1865, Secchi began classifying stars into spectral types, laying groundwork for stellar spectroscopy. By the late 19th century thousands of photographic plates of images of planets, stars, and galaxies had been created.

Image source: Angelo Secchi

The first evidence of helium was observed on August 18, 1868, as a bright yellow spectral line with a wavelength of 587.49 nanometers in the spectrum of the chromosphere of the Sun.

Image source: Helium

Edward Pickering discovered the first spectroscopic binary in 1899 when he observed the periodic splitting of the spectral lines of the star Mizar in a 104-day period.

Image source: Binary star

In Potsdam in 1906, the Danish astronomer Ejnar Hertzsprung published the first plots of color versus luminosity for stars. In 1913, the Hertzsprung–Russell diagram was developed, propelling the astrophysical study of stars during a century of rapid advances.

Image source: Ejnar Hertzsprung

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 Sun was found to be part of a galaxy made up of more than 10 billion stars.

Image source: Milky Way

Cecilia Payne-Gaposchkin first proposed that stars were made primarily of hydrogen and helium in her 1925 doctoral thesis, a foundational insight of stellar astrophysics.

Image source: Cecilia Payne-Gaposchkin

A refined scheme for stellar classification was published in 1943 by William Wilson Morgan and Philip Childs Keenan, known as the MK classification system still used today.

Image source: Stellar classification

Physical cosmology made huge advances during the 20th century, with the hot Big Bang model heavily supported by evidence such as redshifts of very distant galaxies and radio sources, the cosmic microwave background radiation, Hubble's law and cosmological abundances of elements.

Image source: Physical cosmology