c. 3000 BCE Approximate date ancient astronomy

First Stonehenge monument constructed

The first henge monument at Stonehenge dates to about 3000 BCE.

c. 2500 BCE Approximate date ancient astronomy

Solar-aligned Stonehenge stone circle erected

Stonehenge’s central stones were arranged to align with solstitial movements of the Sun.

c. 2450 BCE Approximate date calendar history

Egyptian calendars documented by the Old Kingdom

Calendars based on lunar cycles and agricultural seasons had developed by about 2450 BCE.

c. 1600 BCE Approximate date ancient context

Nebra Sky Disc deposited near Nebra

The Nebra Sky Disc was buried on the Mittelberg near Nebra around 1600 BCE.

c. 800 BCE Approximate date ancient astronomy

Early Chinese sunspot observations recorded

NASA’s solar history associates sunspot observations in the Book of Changes with approximately 800 BCE.

c. 500 BCE Approximate date ancient astronomy

Pythagorean astronomy develops

Pythagoras is included in NASA’s chronology of the early mathematical study of astronomy.

432 BCE Year only calendar history

Meton introduces a calendar in Athens

Meton introduced a calendar connecting lunar months with the solar year.

c. 270 BCE Approximate date astronomy theory

Aristarchus proposes a Sun-centered arrangement

Aristarchus estimated the Sun’s size and distance and proposed that Earth moves around the Sun.

c. 250 BCE Approximate date astronomy measurement

Eratosthenes estimates Earth’s size

Eratosthenes used geometrical reasoning to estimate the size of Earth.

250 BCE to 200 BCE Date range ancient astronomy

Chankillo solar observatory operates

Chankillo’s towers and observation points served as a solar calendar in ancient Peru.

240 BCE Year only astronomical observation

Halley’s Comet recorded in China

Chinese observations provide the first reliably recorded appearance of Halley’s Comet.

c. 150 BCE to 100 BCE Date range ancient context

Antikythera mechanism dates to the late Hellenistic period

The National Archaeological Museum dates the mechanism and its astronomical inscriptions to around 150–100 BCE.

c. 135 BCE Approximate date astronomy measurement

Hipparchus identifies precession

Hipparchus identified precession of the equinoxes and estimated the Moon’s distance.

46 BCE Year only calendar history

Roman calendar reform instituted

Julius Caesar reformed the Roman calendar, establishing the basis of the Julian calendar.

c. 150 CE Approximate date astronomy theory

Ptolemy compiles the Almagest

Ptolemy’s astronomical synthesis set out a geocentric mathematical model of planetary motion.

185 CE Year only astronomical observation

Chinese observers record the guest star SN 185

Chinese records describe a guest star associated by modern astronomers with supernova SN 185.

393 CE Year only astronomical observation

Chinese observers record SN 393

Chinese astronomers recorded a guest star interpreted as supernova SN 393.

c. 499 CE Approximate date astronomy theory

Aryabhatiya composed

Aryabhata composed the Aryabhatiya, an influential work on mathematics and astronomy.

628 CE Year only astronomy theory

Brahmasphutasiddhanta written

Brahmagupta wrote the Brahmasphutasiddhanta, addressing mathematical and astronomical calculations.

c. 820 CE Approximate date observatory institution

House of Wisdom develops under al-Ma’mun

The Baghdad institution supported the study and transmission of scientific and astronomical knowledge.

c. 833 CE Approximate date astronomy theory

Al-Farghani writes Elements of Astronomy

Al-Farghani described celestial motions in a work later influential in European astronomy.

c. 964 CE Approximate date star catalog

Al-Sufi writes the Book of Fixed Stars

Al-Sufi combined Ptolemaic constellation mapping with Arabic astronomical traditions and observations.

1006 CE Year only astronomical observation

Supernova SN 1006 observed

Observers in several regions recorded the exceptionally bright stellar event now designated SN 1006.

1054-07-04 astronomical observation

Crab supernova recorded

East Asian astronomers recorded the guest star associated with the Crab Nebula.

1066 CE Year only astronomical observation

Halley’s Comet commemorated in the Bayeux Tapestry

The Bayeux Tapestry depicts the comet’s appearance around the Norman conquest.

1280 CE to 1350 CE Date range solar science

Wolf Minimum of solar activity

Tree-ring evidence indicates a prolonged interval of reduced solar activity.

1437-03-11 astronomical observation

Korean astronomers record a nova

Korean observers recorded a guest star that faded after roughly two weeks.

1543 CE Year only astronomy theory

Copernicus publishes his heliocentric model

De revolutionibus orbium coelestium presented a mathematical planetary model centered on the Sun.

1572 CE Year only astronomical observation

Tycho Brahe observes a new star

Tycho Brahe and East Asian observers recorded the supernova now designated SN 1572.

1596 CE Year only astronomical discovery

Mira’s variability discovered

David Fabricius recognized changes in the brightness of the star later named Mira.

1604 CE Year only astronomical observation

Kepler’s supernova observed

European and East Asian observers recorded the supernova now designated SN 1604.

1608 CE Year only astronomy instrument

Early telescope developed in the Netherlands

Dutch lensmakers developed the telescope, opening a new route to astronomical observation.

1609 CE Year only astronomy theory

Kepler publishes his first two planetary laws

Kepler described elliptical planetary orbits and the equal-area law using Tycho Brahe’s observations.

1610-01-07 astronomical discovery

Galileo begins observations of Jupiter’s moons

Category: Discoveries and Scientific Results › , type: Discovery

Galileo observed points of light near Jupiter that subsequent observations established as orbiting moons.

1610-04-19 astronomy theory

Kepler suggests a solar influence on comet tails

In a letter to Galileo, Kepler proposed that a solar breeze pushes comet tails away from the Sun.

1613 CE Year only solar science

Galileo publishes Letters on Sunspots

Galileo argued that sunspots are features of the Sun rather than bodies passing in front of it.

1619 CE Year only astronomy theory

Kepler’s third planetary law published

Kepler related a planet’s orbital period to the size of its orbit.

1645 CE to 1715 CE Date range solar science

Maunder Minimum

Solar observations show an extended period with unusually few sunspots.

1687 CE Year only astronomy theory

Newton publishes the Principia

Newton’s Principia presented laws of motion and universal gravitation.

1705 CE Year only astronomy theory

Halley predicts a comet’s return

Edmond Halley linked earlier comet apparitions and predicted a future return of the same object.

1718 CE Year only astronomy measurement

Halley reports stellar proper motions

Comparing stellar positions across centuries, Halley showed that some apparently fixed stars move.

1724 CE to 1734 CE Date range observatory institution

Jai Singh II builds masonry observatories

Five Jantar Mantar observatories supported positional astronomy in northern India.

1750 CE Year only astronomy theory

Thomas Wright publishes a model of the Milky Way

Wright explained the Milky Way’s appearance in terms of a structured distribution of stars.

1758-12-25 astronomical observation

Predicted return of Halley’s Comet observed

Johann Georg Palitzsch detected the returning comet whose reappearance Halley had predicted.

1781-03-13 astronomical discovery

Uranus discovered

Category: Discoveries and Scientific Results › , type: Discovery

William Herschel observed the object subsequently recognized as the planet Uranus.

1801-01-01 astronomical discovery

Ceres discovered

Category: Discoveries and Scientific Results › , type: Discovery

Giuseppe Piazzi discovered Ceres, the first recognized asteroid and now classified as a dwarf planet.

1802 CE Year only solar science

Dark lines observed in the solar spectrum

William Hyde Wollaston noticed dark features in dispersed sunlight.

1817 CE Year only solar science

Fraunhofer investigates solar spectral lines

Joseph von Fraunhofer labeled and systematically studied dark lines in the solar spectrum.

1827-02-09 observatory institution

First issue of MNRAS published

Category: Organizations and People › , type: Organisation founded

The Monthly Notices of the Royal Astronomical Society began publication.

1838 CE Year only astronomy measurement

Bessel measures stellar parallax

Friedrich Bessel measured the distance to 61 Cygni using its annual parallax.