Eclipse Calculations
Aryabhata gives a scientific explanation of solar and lunar eclipses using the shadows of Earth and the Moon.
Astronomy topic guide · World History Database
History of Solar System Discoveries
The known Solar System has expanded repeatedly as instruments and spacecraft improved. Telescopes revealed new planets and moons, mathematical astronomy predicted Neptune, photographic surveys found Pluto and many small bodies, and planetary missions transformed points of light into complex worlds. Discoveries in the Kuiper Belt changed the classification of Pluto and revealed a broad population of icy objects beyond Neptune. The database records below bring these developments together in chronological order.
What this chronology covers
Solar System history now combines Earth-based observing with direct exploration. Telescopes discovered planets, moons, asteroids and distant icy bodies; spectroscopy revealed composition; radar refined sizes and orbits; and spacecraft supplied close-range images and measurements. Missions to the planets and small bodies have repeatedly changed models of planetary formation and evolution. The records on this page therefore include both discovery events and the observational milestones that changed what astronomers knew about familiar worlds.
965matching astronomy records
2,423records in the complete astronomy database
Selected database timeline
The records below are drawn from the existing World History Database astronomy collection and arranged chronologically. For very broad subjects, the page shows a substantial selection rather than duplicating the entire parent database.
Halleys Comet
The 1145 apparition is recorded by the monk Eadwine
Halleys Comet
The 1301 apparition may have been seen by the artist Giotto di Bondone, who represented the Star of Bethlehem as a fire-colored comet in the Nativity section of his Arena Chapel cycle, completed in 1305
Planetary Model
Nilakantha Somayaji presents an improved planetary model that gives Mercury and Venus motions around the Sun while retaining an Earth-centred framework.
Copernican System
Outlines the Copernican system of the solar system
De Nova Stella
Uses the stars absent parallax to place it beyond the Moon.
Discovery of Comets
Tycho Brahe uses parallax measurements to show that comets must lie beyond the Moon
Discovery of Planetary Motion
Finding that an elliptical orbit fit the Mars data, concludes that all planets move in ellipses, with the sun at one focus-Keplers first law of planetary motion
Law of Planetary Motion
Finding that an elliptical orbit fit the Mars data, concludes that all planets move in ellipses, with the sun at one focus-Keplers first law of planetary motion
Copernican System
Publication of "The Starry Messenger", claims the Earth revolves around the Sun. Galileo's observations of the phases of Venus proved that it orbited the Sun and lent support to (but did not prove) the heliocentric model
Discovery of Moon
Uses the newly invented telescope to discover mountains & continents on the moon
Discovery of Saturn
The first observation of Saturn through a telescope is made by Galileo Galilei, his first telescope is so crude that he wasnt able to distinguish the planets rings; instead he thought the planet might have ears or two large moons on either side
Discovery of Venus
Galileo's observations of the phases of Venus proved that it orbited the Sun and lent support to (but did not prove) the heliocentric model. Galileo observes that Venus exhibited a full set of phases similar to that of the Moon
Medicean Stars Named
Galileo names Jupiter's newly discovered satellites the Medicean Stars in honour of the ruling Medici family.
Callisto
The name is suggested by Simon Marius soon after the moons discovery
First Telescopic Observation of Jovian Satellites
Observes three points of light close to Jupiter, beginning the discovery of its major moons.
Observation of Galilean Moons
Independently observes Jupiter's four large moons at about the same time as Galileo.
Discovery of Callisto
Observes the fourth Galilean moon, later named Callisto.
Jovian Moons Recognized as Satellites
Concludes that four observed bodies orbit Jupiter rather than the Earth.
Sidereus Nuncius
Publishes telescopic observations of Jupiter's satellites in Sidereus Nuncius.
Jupiter Moons
Publishes support for Galileo's discovery of satellites orbiting Jupiter.
Jovian Moon Period Studies
Galileo begins systematic study of the orbital periods of Jupiter's four large moons.
Longitude Method Using Jovian Moons
Galileo proposes using predicted eclipses of Jupiter's moons as a celestial clock for determining longitude.
Discovery of Neptune
Galileo also observed the planet Neptune in 1612, but did not realize that it was a planet
Naming of Jupiter Moons
Publishes the names Io, Europa, Ganymede and Callisto for Jupiter's four large moons.
Transit of Mercury Prediction
Kepler's Rudolphine Tables predict that Mercury will cross the face of the Sun in November 1631.
Transit of Venus Prediction
Kepler's Rudolphine Tables predict a transit of Venus for 1631, although the event is not visible from Europe.
Jovian Nomenclature
Later astronomical naming conventions preserve mythological moon names.
Discovery of AU
Measured the distance between the Earth and the Sun using the method of Aristarchus of Samos, the value he calculated was 60% of the true value 243 times the distance to the Moon; the true value is about 384 times
Transit of Mercury Observed
Observes Mercury crossing the Sun as predicted by Kepler.
Transit of Venus Prediction
Horrocks corrects earlier calculations and predicts that Venus will transit the Sun in December 1639.
Transit of Venus Observed
Horrocks observes the first recorded transit of Venus from Much Hoole after projecting the Sun's image safely.
Transit of Venus Observed
Crabtree independently observes the 1639 transit of Venus after Horrocks alerts him to the predicted event.
Detailed Lunar Atlas
Introduces influential names and drawings for visible features of the Moon.
Discovery of Mars
Discovers the Martian south polar cap
Discovery of Saturn
The Dutch astronomer Christiaan Huygens observed Saturn in 1659, and solved the mystery, realizing that the "arms" around Saturn were really a system of rings. He also was the first to observe Saturns moon Titan
Astronomical Unit
Gregory proposes using observations of a planetary transit from widely separated locations to determine the scale of the Solar System.
Jupiter Spot Observation
Observes a conspicuous spot on Jupiter, contributing to early studies of the planet's changing atmosphere.
Discovery of M22
Discovers the globular cluster M22 while observing Saturn in Sagittarius.
Jupiter Permanent Spot
Records a persistent oval feature at the latitude associated with Jupiter's later Great Red Spot.
Jupiter Rotation
Uses atmospheric markings to estimate Jupiter's rapid rotation period.
Comet Observations Catalogue
Creates an extensive seventeenth-century reference work on cometary astronomy.
Cometographia
Publishes observations and historical accounts of numerous comets.
Discovery of Lapetus
Discovered by Giovanni Domenico Cassini as he was studying Saturn and its rings, Cassini guessed correctly that Iapetus was tidally locked to Saturn, and that one half of the planet was bright, and the other half was dark
Tables of Jupiter Moons
Improves tables predicting eclipses and motions of Jupiter's satellites.
Mars Parallax Expedition
Observes Mars from Cayenne for comparison with measurements in France.
Mercury Transit Timing
Halley's Mercury transit observations strengthen interest in using accurately timed planetary transits to refine measurements of the Solar System.
Transit of Mercury
Halley observes a transit of Mercury from Saint Helena and carefully records the event for later astronomical analysis.
Cometary Orbits
Applies Newtonian gravity to cometary paths and later predicts comet return.
Halley's Comet
Halley is classified as a periodic or short-period comet; one with an orbit lasting 200 years or less. After a rough estimate of the perturbations the comet would sustain from the gravitational attraction of the planets, he predicted its return for 1758
Halley's Comet
This calculation enabled him to determine that the orbital elements of a second comet that had appeared in 1682 were nearly the same as those of two comets that had appeared in 1531 (observed by Petrus Apianus) and 1607 (observed by Johannes Kepler). Halley concluded that all three comets were
Halley's Comet
same object returning every 76 years, a period that has since been amended to every 75-76 years.
Halley's Comet
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Synopsis of the Astronomy of Comets
Publishes cometary orbit calculations accounting for perturbations by Jupiter and Saturn.
Synopsis of the Astronomy of Comets
Halley publishes his cometary calculations and predicts that the comet seen in 1682 will return in 1758.
Transit of Venus Method
Halley publishes a method for using future transits of Venus to calculate the Earth-Sun distance more accurately.
Aberration of Light
Uses precision astronomy influenced by earlier Jovian satellite timing work.
Transit of Mercury
Messier documents the transit of Mercury
Milky Way
Kant conjectures that some of the nebulae visible in the night sky might be separate "galaxies" themselves, similar to our own. In a treatise Immanuel Kant draws on earlier work by Thomas Wright, speculates (correctly) that the Milky Way might be a rotating body of a huge number of stars, held together by gravitational forces akin to the Solar System but on much large
Milky Way
In a treatise Immanuel Kant draws on earlier work by Thomas Wright, speculates (correctly) that the Milky Way might be a rotating body of a huge number of stars, held together by gravitational forces akin to the Solar System but on much large
Comet Return Prediction
Calculates that Jupiter and Saturn will delay the predicted return of Halley's Comet.
Halleys Comet
Edmund Halley determines that the orbital elements of a comet which had appeared in 1682, were nearly the same as those of two comets which had appeared in 1531 and 1607, Halley thus concludes that they are the same comet.
Halleys Comet
Edmund Halley returns, as predicted in 1682, Halley's Comet last appeared in the inner Solar System in 1986 and will next appear in mid-2061.
Halleys Comet
Halley's Comet is the best-known short-period comet and is visible from Earth every 75 to 76 years.
Halley's Comet Return
Calculates perturbations that help predict the return of Halley's Comet under Newtonian gravity.
Halleys Comet
Halleys prediction of the comets return proved to be correct, although it was not seen until as late as 25 December 1758 by Johann Georg Palitzsch, a German farmer and amateur astronomer
Halley's Comet Return
Observes the predicted return of Halley's Comet, confirming Newtonian celestial mechanics.
Halleys Comet
Halleys prediction of the comets return proved to be correct, although it was not seen until 25 December 1758, by Johann Georg Palitzsch, a German farmer and amateur astronome
Halley's Comet
Halley's predicted comet is observed again, confirming his orbital calculation after his death and strengthening Newtonian celestial mechanics.
Halleys Comet
The comet is first named in Halleys honour by French astronomer Nicolas Louis de Lacaille in 1759
Halleys Comet
The comet is first named in Halleys honour by French astronomer Nicolas Louis de Lacaille in 1759
Transit of Venus Expedition
Attempts to observe the Venus transit during an extended scientific voyage.
Atmosphere of Venus
Lomonosov observes a luminous arc during the transit of Venus and concludes that the planet possesses an atmosphere.
Transit of Venus Expedition
Mason observes the transit of Venus from the Cape of Good Hope after wartime conditions disrupt the expedition's original destination.
Transit of Venus Expedition
Dixon joins Charles Mason in observing the transit of Venus from the Cape of Good Hope for international distance measurements.
Planetary Distances
Publishes a numerical pattern of planetary distances that includes Jupiter's orbit.
Transit of Venus
Le Gentil reaches Pondicherry for the 1769 transit but clouds prevent him from observing the event after years of travel.
Transit of Venus Expedition
Cook's expedition observes the transit of Venus from Tahiti as part of an international effort to determine the astronomical unit.
Transit of Venus Observed
Green makes timed observations of the Venus transit from Tahiti during Cook's scientific expedition.
Transit of Venus Observed
Rittenhouse leads observations of the transit of Venus in Pennsylvania for measurements of the Earth-Sun distance.
Titius-Bode Law
Popularises the numerical planetary-distance rule that includes Jupiter.
Discovery of Uranus
Calls the new planet the Georgian star (Georgium sidus) after King George III
Discovery of Uranus
Discovers Uranus using a home made telescope from his back garden in Bath
Discovery of Uranus
Produces a diagram of the shape of the Galaxy with the Solar System close to the centre
Uranus
The first attempt to describe the shape of the Milky Way and the position of the Sun within it is carried out by William Herschel carefully counting the number of stars in different regions of the sky
Comet Encke
Comet Encke is first recorded by Pierre Mechain, a periodic comet that completes an orbit of the Sun once every 3.3 year
Discovery of Oberon
Herschel discovers a new moon of Uranus, Oberon
Discovery of Titania
Herschel discovers a new moon of Uranus, Titania
Discovery of Enceladus
Herschel discovers a new moon of Saturn, Enceladus
Discovery of Mimas
Herschel discovers a new moon of Saturn, Mimas, only 250 miles in diameter
Discovery of Neptune
There is evidence that Neptune was seen and recorded by Galileo Galilei in 1613, Jerome Lalande in 1795 and John Herschel in 1830 but none is known to have recognized it as a planet at the time
Jupiter-Saturn Inequality
Explains the long-period inequality in the motions of Jupiter and Saturn through gravitational perturbations.
Discovery of Ceres
Discovers the Ceres asteroid
Celestial Mechanics
Publishes celestial-mechanics work treating gravitational perturbations involving Jupiter.
Comet Encke
Not recognized as a periodic comet until 1819 when its orbit was computed by Johann Franz Encke
Death of Frederick William Herschel
Death of Frederick William Herschel, died in his 84th year, which is the same number of years Uranus takes to orbit the Sun
Herschel Museum of Astronomy
Herschels house at 19 New King Street in Bath, Somerset where he made many telescopes and first observed Uranus, is now home to the Herschel Museum of Astronomy
Great Red Spot Drawing
Makes an early detailed drawing of a large spot on Jupiter later associated with the Great Red Spot.
Encke Gap
Encke describes a broad variation in the brightness of the A Ring of Saturn. The Encke Gap was later named in honor of his observations of Saturns rings
Rings of Saturn
Encke describes a broad variation in the brightness of the A Ring of Saturn. The Encke Gap was later named in honor of his observations of Saturns rings
1st Photograph of Moon
Takes the 1st photograph of the moon
Discovery of Neptune
In an 1846 letter to Wilhelm Struve, John Herschel states that he observed Neptune during a sweep of the sky on July 14, 1830
Triton Observation
Lassell begins follow-up observations confirming that the newly found object moves with Neptune as a satellite.
Prediction of Neptune
Predicts Neptune's position from gravitational perturbations in Uranus's orbit.
Prediction of Neptune
Independently calculates a possible planet disturbing Uranus's orbit.
Discovery of Neptune
Observes Neptune near Le Verrier's predicted position.
Discovery of Triton
Lassell discovers Triton, Neptune's largest moon, only seventeen days after Neptune itself is identified as a planet.
Discovery of Enceladus
Herschel discovered two moons of Saturn, Mimas and Enceladus; as well as two moons of Uranus, Titania and Oberon, he did not give these moons their names; rather, they were named by his son John in 1847 and 1852, respectively, well after his death
Discovery of Mimas
Herschel discovered two moons of Saturn, Mimas and Enceladus; as well as two moons of Uranus, Titania and Oberon, he did not give these moons their names; rather, they were named by his son John in 1847 and 1852, respectively, well after his death
Triton Orbit
Continued observations establish Triton as a genuine moon of Neptune rather than a background star.
Discovery of Oberon
Herschel discovered two moons of Saturn, Mimas and Enceladus; as well as two moons of Uranus, Titania and Oberon, he did not give these moons their names; rather, they were named by his son John in 1847 and 1852, respectively, well after his death
Discovery of Titania
Herschel discovered two moons of Saturn, Mimas and Enceladus; as well as two moons of Uranus, Titania and Oberon, he did not give these moons their names; rather, they were named by his son John in 1847 and 1852, respectively, well after his death
Great Red Spot Drawing
Records a drawing of a large Jovian spot during renewed nineteenth-century observations of Jupiter.
Orbit of Mercury
Le Verrier was the first to report that the slow precession of Mercurys orbit around the Sun could not be completely explained by Newtonian mechanics and perturbations by the known planets
Mercury Perihelion Anomaly
Reports the unexplained advance of Mercury's perihelion, later explained by general relativity.
Vulcan Hypothesis
Le Verrier proposes an unseen planet inside Mercury's orbit as one possible explanation for the unexplained advance of Mercury's perihelion.
Reddish Jovian Oval
Describes a reddish elliptical marking in Jupiter's southern hemisphere during telescopic observations.
Transit of Venus Photography
Janssen uses his photographic revolver during the transit of Venus to record a rapid sequence of solar images.
Deimos
Asaph Hall discovers Phobos and Deimos, the moons of Mars
Mars
Asaph Hall discovers Phobos and Deimos, the moons of Mars
Phobos
Asaph Hall discovers Phobos and Deimos, the moons of Mars
Great Red Spot Tracking
Begins systematic observations of Jupiter's Great Red Spot and its changing longitude.
Jupiter Rotation
Uses atmospheric markings to refine estimates of Jupiter's rotation.
Belgian Venus Transit Observations
The programme contributes measurements intended to refine the astronomical unit.
Belgian Venus Transit Programme
Supports measurement of the astronomical unit through coordinated observations.
Transit of Venus Expedition
Organizes Belgian observations of the transit of Venus.
Transit of Venus Expeditions
Organizes Belgian expeditions to observe the transit of Venus.
Birth of Edwin Powell Hubble
Birth of Edwin Powell Hubble
Mercury Rotation
Schiaparelli reports that Mercury appears to rotate once in about 88 days, suggesting synchronous rotation with its orbital period.
Jupiter Photography
Photographs and studies Jupiter with the large refractor at Lick Observatory.
Discovery of Amalthea
Discovers Amalthea, the fifth known moon of Jupiter and the last satellite found visually.
Discovery of Elara
Discovers Elara, an outer irregular moon of Jupiter, using photographic observations.
Discovery of Patroclus
Discovers Patroclus, an asteroid occupying Jupiter's trailing Trojan region.
Discovery of Pluto
Percival Lowell begins an extensive search for a possible ninth planet, which he calls Planet X.
Discovery of Achilles
Discovers Achilles, the first recognized asteroid sharing Jupiter's orbit near a stable Lagrange point.
Discovery of Hektor
Discovers Hektor, a large asteroid in Jupiter's leading Trojan swarm.
Pasiphae Identified as Jovian Satellite
Identifies Pasiphae, a distant retrograde satellite moving around Jupiter.
Discovery of Pluto
Lowell and William H. Pickering suggest several possible celestial coordinates for the predicted Planet X.
Sinope Added to Jupiter System
Finds Sinope, extending the known family of distant retrograde Jovian satellites.
Discovery of Pluto
Lowell Observatory captures faint images of Pluto, but the object is not recognised as the predicted planet.
Mercury Perihelion
Explains Mercury's anomalous perihelion advance using the emerging general theory of relativity.
Discovery of Pluto
Lowell continues the search for Planet X until his death in 1916 without identifying Pluto.
Asteroid Belgica
Discovers the asteroid later numbered and named 1052 Belgica.
Discovery of Pluto
Tombaugh is assigned to systematically photograph the night sky and compare paired plates with a blink comparator in the renewed search for Planet X.
Discovery of Pluto
Lowell Observatory director Vesto Melvin Slipher assigns Clyde Tombaugh the task of searching for Planet X.
Pluto
Venetia Burney's proposed name Pluto is forwarded to Lowell Observatory and becomes the preferred name for the newly discovered world.
Discovery of Pluto
Tombaugh exposes one of the photographic plates later used, with the January 29 plate, to identify Pluto's motion.
Discovery of Pluto
Tombaugh exposes the second of the two photographic plates later used to identify Pluto's motion against background stars.
Discovery of Pluto
Tombaugh identifies Pluto as a moving object while comparing photographic plates taken on January 23 and January 29.
Discovery of Pluto
Using a blink comparator, Tombaugh identifies a moving object on plates taken January 23 and January 29, discovering Pluto.
Discovery of Pluto
News of Pluto's discovery is telegraphed from Lowell Observatory to the Harvard College Observatory.
Discovery of Pluto
Eleven-year-old Venetia Burney suggests the name Pluto after hearing of the newly discovered world.
Naming of Pluto
Eleven-year-old Venetia Burney suggests the name Pluto during breakfast after hearing news of the newly discovered planet.
Naming of Pluto
Oxford astronomer Herbert Hall Turner forwards Venetia Burney's proposed name Pluto to astronomers at Lowell Observatory.
Naming of Pluto
Lowell Observatory director Vesto Slipher announces Pluto as the proposed name for the newly discovered world.
Jupiter Atmospheric Molecules
Identifies methane and ammonia absorption in spectra of Jupiter and other giant planets.
Methane in Neptune Atmosphere
Spectroscopic work identifies strong methane absorption in Neptune's atmosphere and helps explain the planet's visible colour.
Neptune Atmospheric Spectrum
Adel analyses giant-planet spectra and confirms strong methane absorption features in Neptune's atmosphere.
Asteroid 1373 Cincinnati
Discovers asteroid 1373 Cincinnati
Discovery of Lysithea
Discovers Lysithea, an irregular satellite of Jupiter.
Related astronomers
AryabhataProfile and database timelineBhaskara IIProfile and database timelineNicolaus CopernicusProfile and database timelineTycho BraheProfile and database timelineGalileo GalileiProfile and database timelineJohannes KeplerProfile and database timelineEdmond HalleyProfile and database timelineWilliam HerschelProfile and database timeline
Sources and editorial provenance
Compiled and edited by World History Database
Historical chronology compiled from the World History Database and checked against major scientific and historical reference sources.
Last reviewed: September 2026.
- Royal Museums Greenwich — History of astronomy
- Royal Museums Greenwich — History of the telescope
- NASA Science — Hubble timeline
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- Event Horizon Telescope — first black-hole image
- NASA Webb — mission science and discoveries