Pre-historic , constructed by Neolithic populations, located in
Aswan,
Upper Egypt. found on
Mittenberg hill in Germany and dated to . The initial development of astronomy was driven by practical needs like agricultural calendars. Before recorded history archeological sites such as
Stonehenge provide evidence of ancient interest in astronomical observations. Evidence also comes from artefacts such as the
Nebra sky disc inlaid with symbols interpreted as a sun, moon, and stars including
a cluster of seven stars. Megalithic structures located in
Nabta Playa, Upper Egypt featured astronomical calendar arrangements in alignment with the heliacal rising of
Sirius and supported calibration the yearly calendar for the annual Nile flood.
Classical (7th century BCE) was an early astronomical instrument. Its use of
sexagesimals (e.g. 12, 24, 60, 360) is still being used today through having been broadly adopted for
timekeeping and
astrometry. Civilizations such as
Egypt,
Mesopotamia,
Greece,
India,
China independently but with cross-cultural influences created astronomical observatories and developed ideas on the nature of the Universe, along with calendars and astronomical instruments. A key early development was the beginning of mathematical and scientific astronomy among the Babylonians, laying the foundations for astronomical traditions in other civilizations. The Babylonians discovered that
lunar eclipses recurred in the
saros cycle of 223
synodic months. Following the Babylonians, significant advances were made in
ancient Greece and the
Hellenistic world. Greek astronomy sought a rational, physical explanation for celestial phenomena. In the 4th century BC,
Heracleides Ponticus was the first to proposed that the Earth rotates on its own axis. In the 3rd century BC,
Aristarchus of Samos estimated the
size and distance of the Moon and Sun, and he proposed a model of the
Solar System where the Earth and planets rotated around the Sun, now called the
heliocentric model. In the 2nd century BC,
Hipparchus calculated the size and distance of the Moon and invented the earliest known astronomical devices such as the
astrolabe. He also observed the small drift in the positions of the equinoxes and solstices with respect to the fixed stars that we now know is caused by
precession. The
Antikythera mechanism (–80 BC) was an early
analog computer designed to calculate the location of the
Sun,
Moon, and
planets for a given date. Technological artifacts of similar complexity did not reappear until the 14th century, when mechanical
astronomical clocks appeared in Europe.
Post-classical After the classical Greek era, astronomy was dominated by the
geocentric model of the Universe, or the
Ptolemaic system, named after
Claudius Ptolemy. His 13-volume astronomy work, named the
Almagest in its Arabic translation, became the primary reference for over a thousand years. In this system, the Earth was believed to be the center of the Universe with the Sun, the Moon and the stars rotating around it. While the system would eventually be discredited, it gave the most accurate predictions for the positions of astronomical bodies available at that time. Earlier indigenous traditions, such as those recorded in the Vedāṅga Jyotiṣa, provided calendrical foundations, while Greek astronomical models were later integrated by scholars including
Āryabhaṭa,
Varāhamihira, and Brahmagupta. Āryabhaṭa notably improved methods for calculating planetary motions and eclipses. In the later medieval period, the
Kerala school contributed to astronomy through refined observational practices and more accurate planetary and eclipse calculations. in the
Compilatio astronomica, 1493.
Islamic astronomers collected and translated
Indian,
Persian and
Greek texts, adding their own work.
Astronomy flourished in the medieval Islamic world. Astronomical
observatories were established there by the early 9th century. In 964, the
Andromeda Galaxy, the largest
galaxy in the
Local Group, was described by the Persian Muslim astronomer
Abd al-Rahman al-Sufi in his
Book of Fixed Stars. The
SN 1006 supernova, the brightest
apparent magnitude stellar event in the last 1000 years, was observed by the Egyptian Arabic astronomer
Ali ibn Ridwan and
Chinese astronomers in 1006. Iranian scholar
Al-Biruni observed that, contrary to
Ptolemy, the Sun's
apogee (highest point in the heavens) was mobile, not fixed. Arabic astronomers introduced many
Arabic names now used for individual stars. The ruins at
Great Zimbabwe and
Timbuktu may have housed astronomical observatories. In Post-classical West Africa, astronomers studied the movement of stars and relation to seasons, crafting charts of the heavens and diagrams of orbits of the other planets based on complex mathematical calculations.
Songhai historian
Mahmud Kati documented a
meteor shower in 1583. In medieval Europe,
Richard of Wallingford (1292–1336) invented the first astronomical clock, the
Rectangulus which allowed for the measurement of angles between planets and other astronomical bodies, as well as an
equatorium called the
Albion which could be used for astronomical calculations such as
lunar,
solar and
planetary
longitudes.
Nicole Oresme (1320–1382) discussed evidence for the rotation of the Earth.
Jean Buridan (1300–1361) developed the
theory of impetus, describing motions including of the celestial bodies. For over six centuries (from the recovery of ancient learning during the late Middle Ages into the Enlightenment), the
Roman Catholic Church gave more financial and social support to the study of astronomy than probably all other institutions. Among the Church's motives was finding the
date for Easter.
Copernicus During the
Renaissance,
Nicolaus Copernicus proposed a heliocentric model of the solar system. While his model maintained circular orbits, it was sufficient to calculate the size of planetary orbits and their period. The appealing simplicity of Copernican astronomy led to its adoption among astronomers even before it was confirmed by Galileo's telescopic observations in the 1600s. Analyzing two decades of careful observations by
Tycho Brahe, Kepler devised a system that described the details of the motion of the planets around the Sun. While Kepler discarded the uniform circular motion of Copernicus in favor of elliptical motion, It was
Isaac Newton, with his invention of
celestial dynamics and his
law of gravitation, who finally explained the motions of the planets. Newton also developed the
reflecting telescope. Newton, in collaboration with
Richard Bentley proposed that stars are like the Sun only much further away. The astronomer
William Herschel made a detailed catalog of nebulosity and clusters, and in 1781 discovered the planet
Uranus, the first new planet found.
Friedrich Bessel developed the technique of
stellar parallax in 1838 but it was so difficult to apply that only about 100 stars were measured by 1900. Significant advances in astronomy came about with the introduction of new technology, including the
spectroscope and
astrophotography. In 1814–15,
Joseph von Fraunhofer discovered some 574
dark lines in the spectrum of the sun and of other stars. In 1859,
Gustav Kirchhoff ascribed these lines to the presence of different elements.
Galaxies In the late 1700s
William Herschel mapped the distribution of stars in different directions from Earth, concluding that the universe consisted of the Sun near the center of disk of stars, the
Milky Way. After
John Michell demonstrated that stars differ in intrinsic luminosity and after Herschel's own observations with more powerful telescopes that additional stars appeared in all directions, astronomers began to consider that some of the fuzzy
spiral nebulae were distant
island Universes. The existence of galaxies, including the Earth's galaxy, the
Milky Way, as a group of stars was only demonstrated in the 20th century. In 1912,
Henrietta Leavitt discovered
Cepheid variable stars with well-defined, periodic luminosity changes which can be used to fix the star's true luminosity which then becomes an accurate tool for distance estimates. Using Cepheid variable stars,
Harlow Shapley constructed the first accurate map of the Milky Way.
Cosmology Albert Einstein's 1917 publication of
general relativity began the modern era of theoretical models of the universe as a whole. In 1922,
Alexander Friedman published simplified models for the universe showing static, expanding and contracting solutions. was discussed but no experimental evidence was available to support it. From the 1940s on, nuclear reaction rates under high density conditions were studied leading to the development of a successful model of
big bang nucleosynthesis in the late 1940s and early 1950s. Then in 1965
cosmic microwave background radiation was discovered, cementing the evidence for the Big Bang. and
neutron stars. These have been used to explain phenomena such as
quasars and
pulsars.
Space telescopes have enabled measurements in parts of the electromagnetic spectrum normally blocked or blurred by the atmosphere. The
LIGO project
detected evidence of
gravitational waves in 2015. ==Observational astronomy==